I tend to reach for the five volume Sear catalog and RIC first, but I was wondering what references everyone else here uses. I am a bit of a numismatic bibliophile, I always want more coin books and I have a special weakness for multi-volume sets. I hope this thread doesn't end up costing me money.
I find David L. Vagi, Coinage and History of the Roman Empire very helpful, two volumes one deals with coinage and the other one history which also makes reference to the coins, big read and not to expensive. One note though the coinage one is not that comprehensive, more a snapshot of the prices of most of the common types.
I rely most on Sear, RIC, and Seaby's RSC. I seem to refer to these at least once a day when searching for coins in online auctions. I also like Aorta, it contains a lot of interesting information. However, since it does not mention the RIC numbers it is not very useful for cross referencing. I always like to have confirmation from at least 2 of RIC Sear and RSC before I trust an attribution.
My most-used books are the first three volumes of Sear (but not four and five), all of RIC, all of BMC, and Failmezger "Roman Bronze Coins: From Paganism to Christianity, AD 294-364". Because I like late Roman coins, I use " Late Roman Coins" (in the Dumbarton Oaks collection) by Grierson and Mays quite a bit. As well as extensive photographic coverage, it has a great deal of commentary. Those are books that are excellent for looking up coins. If you want a general overview so you understand the big picture, there are other books which deserve to be read, several times. There are many volumes of introductions to coinage (as opposed to just coins). A great one is "Coinage in the Roman World" by Andrew Burnett (formerly Curator of Coins at the BM, now deputy director). It is not large, but well written with 187 important types illustrated. "Roman Coins" by C.H.W. Sutherland is a large book very well illustrated (572 photos, enlarged, most two photos per coin but a few with only one when it is a special reverse) with commentary on the development of the coinage. You won't use it to look up coins, but to read about Roman coins in general during the various time periods. There are many other books I could recommend, if, say, you wanted to know about coins in Roman Britain, or how the Roman economy worked, or how scholars use coins to study history, or lists of historical events and the coins that reference those events, or the coinage of the first century, or any number of other topics. If you can tear yourself away from the computer and the process of buying coins, you could sit by the fire and read an enjoyable and informative book and learn a lot you didn't know abut Roman coins.
For cataloguing: RIC II.1, BMCRE II, RSC II, and RPC II. For background info: The Metallurgy of Roman silver Coinage: From the Reform of Nero to the Reform of Trajan - K. Butcher and M. Ponting, Coinage and Finances in the Reign of Domitian - Ian Carradice, A Dictionary of Ancient Roman Coins - John Melville Jones, Roman coins - C.H.V. Sutherland, Coins of the Roman Empire - R.A.G. Carson, Coinage in Roman Syria - K. Butcher, and Coinage in the Roman Economy - K. Harl. I still glance at my volumes of Sear, but not very often.
I usually look at Antoninus Pius denarii. I end up cross referencing Wildwinds (should probably get a copy of RIC III), Cohen, and Le trésor numismatique de Réka-Devnia.
I focus mainly on Late Roman bronze coins but sometimes dabble in denarii and use the standard RIC volumes and occasionally use Sear, BMC, RSC and Hunter. However, there are many specialty works that focus more narrowly and more completely. For Lyons, I use the books by Pierre Bastien covering the period from A.D. 285- 413 in five books; but there are two supplements. 1-Le monnayage de l'atelier de Lyon-Dioclétien et ses corégents avant la réforme monétaire (285-294) 2-Le monnayage de l'atelier de Lyon-De la réforme monétaire de Dioclétien à la fermeture temporaire de l'atelier en 316 (294-316) 3-Le monnayage de l'atelier de Lyon-De la réouverture de l'atelier en 318 à la mort de Constantin (318-337) 4-Le monnayage de l'atelier de Lyon-De la mort de Constantin à la mort de Julien (337-363) 1985, 263p 5-Le monnayage de l'atelier de Lyon- Du règne de Jovien à la mort de Jovin (363-413) 1987, 271p 6-Supplément I (Bastien-Amandry-Gauthier) (274-413) 7-Supplément II (Amandry-Estiot-Gauthier) (43 AV JC-418 ap. J.C) He also wrote a book on Magnentius- Le monnayage de Magnence. These are not all the Bastien books either, just the ones I use. A nice hoard of mainly VLPP’s from Siscia Bikić-Do Hoard Brenot, C., "Le trésor de Bikić-Do", [in:] Sirmium VIII. Études de Numismatique Danubienne. Trésors, Lingots, Imitations. Monnaies de Fouilles IVe au XIIe Siècle, Rome-Belgrade 1978, pp. 5-98. For the London mint- Cloke, H. J., Toone, L. The London Mint of Constantius and Constantine, Spink, London 2015. For Arles Mint- Ferrando, Ph., L'atelier monétaire d'Arles: de Constantin le Grand à Romulus Augustule (313-476), Arles 2010. For Maxentius issues- Drost, V., Le monnayage de Maxence (306-312 aprés J.-C.), Zürich 2013. For the Christian persecution issues- van Heesch, J., "The Last Civic Coinages and the Religious Policy of Maximinus Daza (AD 312)", Numismatic Chronicle 1993, pp. 65-75. For some Trier issues- Alten, D., Zschucke, C.-F., Die römische Münzserie Beata Tranquillitas in der Prägestätte Trier 321-323, Petermännchen-Verlag, Trier 2004. Zschucke, C.-F., Die Bronze-Teilstück-Prägungen der römischen Münzstätte Trier, Petermännchen-Verlag, Trier 2002. For the Aquileia mint Paolucci, R., Zub, A., La monetazione di Aquileia romana / The roman imperial coinage of Aquileia, Padova 2000. I have several of the Coin Hoards from Roman Britain books, about 6 or 7 the Venera hoard- Venera Hoard Volume I – Gordian III- Quintillus Venera Hoard Volume II- Tacitus and Florian. Venera Hoard Volume IV- Caro – Diocletian 4 books by Gobl called Moneta Imperii Romani or MIR 1. MIR 47 Aurelian (270/275) 2. MIR 36, 43, 44 Valerian, Gallienus, Saloninus,(253-268) Regalianus (260) and Macrianus/ Quietus (260/236) Sometimes I even use Cohen, Maurice and Voetter. I actually collect literature more than coins now.
Only books I have is ERIC II & Emmett. I have many in digital book form, but admit I don't use them much.
I love the five volume Sear (I had them signed by him ) but I also use ERIC II for the odd things and Vagi for the biographies.
Here is, by request, comments on books on how scholars use coins to study history. The primary work (including Greek coins) is by Christopher Howgego, Ancient History from Coins. It is very well-written with 183 coins beautifully illustrated in black and white, but it helps if you already know some ancient history. Howgego is at Oxford and a great expert. That is my top recommendation. An advanced book on Greek coins and history is by Colin Kraay, Greek Coins and History: Some Current Problems, although it is from 1969 and those particular problems are out-of-date. Still, it give you a feeling for the sorts of dating problems, etc. that Greek numismatists confront. If you want a list of Roman coins that reference events, Roman Historical Coins by Clive Foss fills the bill. It has short descriptions of historical events that are referenced on Roman coins and then lists the coin types that refer to the events. It has some photos, probably about 300 coins, but that is only a small fraction of the types. Back when my focus was historical types, it was very good for letting me know what was out there to be collected, but I needed BMC and RIC to see what they looked like. Now you could see them on the web. C.H.V. Sutherland wrote Roman History and Coinage 22 BC - AD 69, a thin hardcover of 131 pages discussing 49 events, some which provoked more than one type. Unfortunately, he died before it was published and some of the types did not get illustrated even though the picture has captions. When I bought it I thought they made an error. The first picture in the book is 1b, even though there is a caption for 1a. He quotes the Latin author describing the event, translates it, and comments on the corresponding coins. This far from an exhaustive list, but will get you started.
Honestly I think the question is too broad. Each collector buys and uses references which are specifically geared towards their own individual tastes. What one may find of use will be useless to another. It might be that you should rephrase the question with some more specifics. What series, what time frame, metals, etc. As a dealer I followed the same path a lot of others have (as that is what we were all told to do), and I built a large and comprehensive library. A few years back I looked at all these books. Most of them I never opened or even used. Why have 50 antiquated books on one topic when they are all rendered useless by, say, Sear? I'm not a book collector, so I sold them all off (not surprisingly they sold for pennies on the dollar for what I paid).
Aethelred, I finally took the plunge and cut back on acquiring coins in order to get books. This was primarily driven by about 10 unattributed Tetrarchy and Constantinian bronzes that I had vague unsubstantiated ideas about. So far I have David Sear's Roman Coins volume 4 and both of his volumes on Greek coins. My interest in Greek coins is all over the place, I really needed a well organized reference. These books have been very helpful and have answered numerous questions beyond the coins themselves plus filling an important void in my enjoyment of the hobby. Thanks all for providing valuable reference suggestions, some of which definately merit further pursuit...
My main focus is on RR/Imperial/Western Empire/Eastern Empire/Byzantine AV coinage/now also AR stuff. ONLY book I have on these are ERIC-II/ Byzntine coinage by Paul Whiting. I have lots of other books, since I collect upto present day AV material.
I'd like to put in a plug for a book which I don't believe has been mentioned and can be very useful for the student/collector of LRB's - "Late Roman Bronze Coinage" by Carson, Hill and Kent (also known as "LRBC" or "CHK") This is a slim volume originally in the same size-format as RIC so it would be unobtrusive on the shelf with RIC volumes. In fact, for a lot of years, before RIC vols VIII & X were published, it was considered a semi-official volume of the RIC. The learning curve for how to interpret the rows and columns of codes for various features is a bit challenging. I am put in mind, somewhat, of the background of cascading columns of characters in the opening title sequence of The Matrix, thinking back on what I thought the first time I opened it and tried to figure out what was going on - it was hard to find for many years but has been re-issued in inexpensive cardcover format in recent years. Another book I get a fair amount of use out of is David Van Meter's "The Handbook of Roman Imperial Coins" (this is possibly the most "bang-for-the-buck" deal in the world of fairly recent ancient coin books). When trying to think of quick reference points - such as the dates of various consecutive and concurrent rulers - it's somewhat of a toss up whether the first book I reach for will be Van Meter or the 1988 4th edition of David Sear's Roman Coins and Their Values. Another volume used almost daily is "Greek Coin Types and Their Identification" by Richard Plant. Well worn (nearly worn out, truth to tell) copies of those three are literally at my elbow, on the same stack of shelving that contains my sets of RIC, RSC, Sear Millennium, Lindgren, Vols I, II & VI of RPC, and the several SNG's and other specialized works that get regular use like Emmett for Alexandria, Spaer and Houghton for Seleukids, Icard for legend fragments, Failmetzger for fine details on the LRB's. Gobl for Sasanian, de Morgan for Elymais, Sydenham on Republican, Bellinger on the Troad & Hellespont. I could go on naming specialist volumes, but you get the idea, I'm sure. Of course, since I was collecting decades before the internet was a thing, I am probably less likely than most to turn to on-line references as a first resort, but I find a few of them crucial to the cataloging work I do - despite being primarily oriented to the use of books.