Warman Books - Ellen T. Shroy - The Warman books are fabulous for identifying glass. They have a company timeline, color timeline, color identification, shape guide and a thumbnail guide. This is one of the most useful books I own. Most glassware books are out of print and therefore, hard to find. They are available at some libraries and well worth the time to review, especially if you just cannot figure out a pattern or color.
Also if you ever run across one at an auction, estate or garage sale in my opinion this book is worth the investment. The Warman Depression Glass 4th Edition I own was purchased at an auction, I paid $25.00, which I thought was expensive, but it was worth the money. The original price on this book in 2006 was $27.99. This book is well utilized by me.