Yes, CHAPTERS is a Scrabble word!

Letter values in Scrabble US: C 3, H 4, A 1, P 3, T 1, E 1, R 1, S 1.

Is it a valid word?

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

a subdivision of a written work; usually numbered and titled
any distinct period in history or in a person's life
a local branch of some fraternity or association
an ecclesiastical assembly of the monks in a monastery or even of the canons of a church
a series of related events forming an episode