CRACK THE BOOKS is an idiom that means to study hard and put in a lot of effort. The crossword solutions for this term are CRAM, READ, and CHAP. Cramming is the act of studying a large amount of material in a short period of time. Reading is the act of looking at written material and understanding it. CHAP is a British slang term for a person, so in this context it could mean to talk to someone knowledgeable about the material being studied.