For half cents I think it depends on your collecting interest. Just attribution, I think either Breen or Cohen are reasonable tools to get the job done. I prefer Cohen as I fear Breen was a little relaxed on the difference between facts and speculation. Personally, I prefer Manley's The Half Cent Die State Book as it has a lot more information on each variety. It's also much more of a complete commentary of the series as oppose to just an attribution guide. The downside is the binding is horrible, mine has a dozen or so pages complete detached from the binding, and the copies are in short supply so they can be expensive.
Thanks for the tips Beef, I'll keep an eye out. And that was my worry about Breen as well. Sort of like a Grellman attributed coin; take it with a grain of salt when it comes to proof v business strike.
For Half Cents either Breen's half cent encyclopedia or Cohen's Little Half Sisters is good. The Breen book is my personal preference because it has more background information in it, and it is more readily available. (around $60) But it is large and heavy. The Cohen book is lighter and easier to carry if you want to take it to a show or LCS (around $70 for the second edition, but I did find a first edition for $51). Greg Helm has a good quickfinders guide for attributing at shows etc, but it has no plates. So you have to have some experience before it is easy to use. The Manley book is quite good with more information on die states, but as mentioned the binding isn't good and it is very difficult to find and costly. I did a search and only found one copy available, at $294.00
My first committed step into varieties, or should I be committed ?!??? This is going to take a while to decipher but thanks to Conder101's tips perhaps I will be able to navigate .
If you have problems just come back and ask. Another bit of advice, until you have some experience stick with the 1816 - 1834 varieties. The 35 - 39's are tougher to figure out. And you will probably want a different book for the 1840 - 57 varieties.
Late dates are impossible without Grellman/Reiver IMHO. The date position reference idea they introduced makes attribution doable with practice. I have tried to use Newcomb for fun, am I clinically insane???, and found it unmanageable. I consider Newcomb's late date work to be an important but incomplete first attempt at organizing the series, no offense to Andrew's but I think his late date attempt was just idle musings. Grellamn/Reiver took Newcomb's work to it's logical conclusion, cleaned up the process of attribution and corrected a lot of understandable mistakes. I consider it essential for late date attribution, no other reference will suffice.
I'm not sure if it is a conclusion or not. One more thing I could see for the next step after Grellman would be micrographs of the points and die lines and other diagnostic features for each variety along the lines of Peterson's Ultimate Guide to Bust Half Dollars. I'm not sure if it would work well as a printed book but it might work well on a computer or tablet. The images wouldn't be of much use for initial attributions, but could be very useful for final confirmation. The identifying features of the late dates are typically too fine to be seen on images of the whole coin, even if enlarged. But if it says "points up from top of E" and you have a sharp image of just that area, it could be show full screen without pixelation and allow you to see exactly where those points are and what they look like.