The book mentioned by Galen is very good, the best one on history of the companies. There are lots of others if you can afford several. There is a paperback on catseyes, can't locate mine at the moment to give you the name. Paul Baumann has one called Collecting Antique Marbles. Another I like is Collecting Early Machine-made Marbles, The M. F. Christensen & Son Company and Christensen Agate Company by Block.
Just depends on what you want to collect or what you want to learn. Edna