I have a copy of a book by Peter Alan Glasser called "Glock" It is a great book, just a little older than some in that when it was written, some of the glock models are not mentioned as they hadn't been developed yet.
I like "The Complete Glock Reference Guide" by Ptooma publications. Also good reading (but a little dated) about Glocks in general is "Glock: the New Wave in Combat Handguns". Also for general Glock reading I like (but some folks done) "The Gun Digest Book of the Glock". I got the first one from Brownell's, but it's also available elsewhere, and I got the other two used on Amazon.