Catalyst is an excellent first place to look for book reviews. Search below using the author's name and key words from the title, then limit your results to the Content Type "Book Review" (on the left side of the page):
Catalyst Articles Search
Reviews in American History
Although many scholarly journals contain reviews, Reviews in American History is the most comprehensive in this field.
"Reviews in American History is a journal of ideas that offers anyone interested in American history a way to stay current with the discipline. Each issue presents in-depth review essays about the latest books in American history. Retrospective essays examining landmark works written by leading historians are also regularly featured. The journal covers all areas of American history, including cutting-edge and more traditional sub-fields."