Minecraft version: 1.12.2
Wizardry version: 4.1.1
Environment: Server

Issue details: Me and my friend started a modded survival server and we added the mod and in the beginning we could open the book fine but after a while every time we try and open it, it crashes our game.

Other mods involved: Rouge like Dungeons, Bookshelf, AbyssalCraft,Hunter Dimension, Industrial Craft and Buildcraft

Link to crash report: https://pastebin.com/9sY7YZh9

Could you tell me what your keybindings are for the next/previous spell keys?

Mouse5 and Mouse4

Ok so they're not keyboard keys, that makes sense. The wizard handbook GUI uses org.lwjgl.input.Keyboard to look up the key names but obviously that doesn't work for mouse buttons (I'm not sure my mouse even has a button 4 and 5), so it crashes. I'll get that fixed for the next update.