A book review would be considered

Aa primary source.
Ba secondary source.
Ca tertiary source.
Deither a secondary or tertiary source, depending on content.

Verified Answer :

It is definitely not a primary source: this would be a book itself.

Now, is it a tertiary source? I don't think so: the author of the review should have read the book and should only be referring to this book in the review.

I think it's a secondary source.