One of the better books to start with IMO is "Miller's 20th Century Glass" by Andy McConnell (not to be confused with Judith Miller's 20th Century Glass). It's out of print, but I bought mine secondhand and was very happy with it. Many books will cover early 20th century glass (Gallé, Lalique, etc), but this one also pays attention to the glass made after WWII.
The only drawback is that certain areas of European glass are not very well covered in the book. It doesn't say much about postwar Czech, Dutch, German, Belgian and French glass, to name a few, so if you want to check those areas out, you'll have to do additional research.
Apart from books, I found that admiring the webposted collections of fellow members on the board is a nice way to explore and learn... and they often link to other collections as well.
Have fun browsing!
Astrid