Went over to the Carolina Coin & Stamp Show today, specifically looking for books about California fractional gold. Alas, the Barber Shop guys, who generally have all the books, didn't have any books on this topic. I would've sworn I saw one or two of the standard references in their previous displays, but the proprietor said he didn't think they'd been carrying them. Not really feeling the urge to buy or sell actual coins today, so I left as I arrived, empty-handed. There was a good turnout of dealers, though, with none of the empty spots I've seen at the last few shows.
You want to find a copy of the book by Breen and Gillio titled California Pioneer Fractional Gold. Many consider it the definitive book on the topic. I found my copy on Abe's books and it wasn't cheap. Currently I see copies available from $189 to $450.
I had naively thought Barber Shop might carry that one. I had forgotten that it had turned into quite such a treasure. All I really wanted was a weight range for one particular token. I intended to buy whatever book could provide that, but I probably wouldn't have gone three figures on it.