Yes, CASEBOOK is a Scrabble word!

Letter values in Scrabble US: C 3, A 1, S 1, E 1, B 3, O 1, O 1, K 5.

Is it a valid word?

CASEBOOK is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

a book in which detailed written records of a case are kept and which are a source of information for subsequent work