A solid book review should contain each of these pieces:
Main ideas of the book
How the book is organized
Analysis of the book's effectiveness: does the author do or prove what she says she will?
Recommendation: who should read this book?
See if you can identify all the elements mentioned in this brief book review:
Krista Sigler. Review of Reid, Susan Emily; Blakesley, Rosalind P., eds, Russian Art and the West: A Century of Dialogue in Painting, Architecture, and the Decorative Arts. H-Russia, H-Net Reviews. April, 2009.
Several databases contain book reviews; check the library description of the database, or look at the advanced search options of a database to search for just book reviews. Some likely sources are listed here to give you options.