To quote a well known meme, "Screw the rules, I have money". If you want wizard spell books to be dangerous in your games, go ahead and allow glyph of warding to work on them, reguardless of their mobile nature. If wizards start using that power to say hey look over here at the explodey book, then have it malfunction and destroy some spellbook pages or something.
The key is to make the rules and the game work the way YOU want them to, don't get bogged down in RAW. Make sure it works that way for PCs as well tho, if you have a wizard in the party, he can trap his spellbook as well.