Ther are really two main priceguides that are widely accepted:

The Chip rack(TCR) is a very extensive and very thick priceguide strickly dealing with Nevada chips.

The Official Casino Chip Priceguide- Covers many other states, (but not all)

Personally, I use them both. I find TCR more extensive. Official Priceguide has pictures and covers other states as well.

Although both books are very good, both also have some shortcomings. As time goes on, prices change because of many reasons. In my humble opinion, I don';t believe a priceguide should have a new issue come out no linger then every two years.

You'll also find there's priceguide for about any chip area you csn think of:

Atlantic City, Colorado, Riverboats, Puerto rico, Montana, Illegals, Northern Midwest, florida, Cruise ships, and many many more.

Here's a link to some of the prioceguides:
http://www.chipguide.com/cgi-bin/search/search.cgi?id=books