Try this:

Put a note/flyer up that states:

Book Missing. Video surveillance footage shows the culprit. Before video is turned over to Police in 24 hours and you get arrested and a blemish put on your record, please return the book to where you found it. No questions asked.

Hint: Thief doesn't know if there was a camera or not! But, now set one up to record and you will know who took it. Does that student pilot want to risk his flying career being tarnished for stealing. When caught don't screw your career by getting charged with assault. Just ensure he slipped in the bathroom.