Yes, CONTENTS is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, N 1, T 1, E 1, N 1, T 1, S 1.

Is it a valid word?

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

a list of divisions (chapters or articles) and the pages on which they start
everything that is included in a collection and that is held or included in something
what a communication that is about something is about
the proportion of a substance that is contained in a mixture or alloy etc.
the amount that can be contained
the sum or range of what has been perceived, discovered, or learned
the state of being contented with your situation in life
something (a person or object or scene) selected by an artist or photographer for graphic representation

Also: table of contents, subject matter, cognitive content, mental object, depicted object.