Yes, REVIEWS is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, V 4, I 1, E 1, W 4, S 1.

Is it a valid word?

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

a new appraisal or evaluation
an essay or article that gives a critical evaluation (as of a book or play)
a subsequent examination of a patient for the purpose of monitoring earlier treatment
(accounting) a service (less exhaustive than an audit) that provides some assurance to interested parties as to the reliability of financial data
a variety show with topical sketches and songs and dancing and comedians
a periodical that publishes critical essays on current affairs or literature or art
a summary at the end that repeats the substance of a longer discussion
(law) a judicial reexamination of the proceedings of a court (especially by an appellate court)
practice intended to polish performance or refresh the memory
a formal or official examination

Also: critical review, review article, follow-up, limited review, go over, brush up, look back.