Mark & Myrna Lighterman & Bob Ginsburg have two very good books Guides To Florida's Gaming Chips, Checks, and Tokens.
Larry Eastman has A guide to California Chips.
Ed Hertel has a good book on Illegal casinos
The Gaming Table is A must for all collectors.
Wayne Threadgill just did a fine book on Hot Springs Illegal casinos.
Howard Herz has several good books. USPC Chips, Hunt co Chips, NV Gaming Checks & chips.
Steve Goodrich has books on Montana & Washington chips.
And some I forgot.