This mod pauses the game when you open the handbook. This was made quickly and I can't garuntee you won't encounter bugs but so far I haven't encountered any problems. Opening the handbook using the escape menu doesn't seem to work though. Anybody is free to mess around with the code or do a better version of this. I have some code that would pause the game when the player would open blockinventories but I commented it out since the handbook pausing is what I was going for and you can't open multiple chests when the game has paused.

This obviously should only work on singleplayer and turn it off if playing multiplayer (It shouldn't work multiplayer but just incase).

I have no idea about mod compatibility but I assume it will be fine as long as harmony is working.