With a retail price of less than $13 (and many used copies available through Amazon for as little as $4.95), the Corning Museum of Glass: A Guide to the Collections is arguably the world's best value in glass art books.
Contents are divided among over a dozen sections (i.e. Glass of the Romans, Asian Glass, Modern Glass, etc.) and each of the almost 200 objects covered have full color photos and almost a half page write up on the importance of the work.
The book might not be quite as thrilling as the new Harry Potter sequel, but as a 200 page introduction to glass art and it's history you'd be hard pressed to find a more complete or enjoyable text at twice the price.