Is it always one reviewer to a given "review"? I see you have multiple books that can be assigned to a given review and wonder if multiple reviewers is also a possibility.
In any case, you'll need at least two more tables to make life easier. I'll assume one reviewer only to start:
(Put your review specfic data here rather than in Books)
ReviewID (auto-entered serial number)
Books::BookID = Books_Reviews::BookID
Reviews::ReviewID = Books_Reviews::ReviewID
Reviews::ReviewerID = Reviewers::ReviewerID
Books_Reviews becomes a "join" table that allows you to link many books to many reviews.
Apologies for not providing more details, but maybe this will help get you started.
Many thanks. No you are right to assume there is only ever one reviewer per book. See what you are getting at re extra tables and will have a go at modifying the DB. Will come back to you if I get stuck. This also covers a related question I didn't include. How to handle issues, groups of accepted reviews selected to go in one printed issue, I see I would handle this the same way with a further table: Issues.