There are several places to find book reviews, here are a few suggestions-
Search the databases by type and you will find a book reviews section in the pull down menu. That list of databases is available here See especially Book Review Index (1965-date) and Book Review Digest Plus (1983-date) and Book Review Digest Retrospective (1908-1982)
Historical Abstracts contains book reviews written since 1955
JSTOR database has full text book reviews going back to the late 19th century in some of the journals included there.
Limiting document types to book reviews is a search option in both these databases.
Combined retrospective index set to journals in history, 1838-1974 This set is in the reference collection on the main floor
Britain and the World: Historical Journal of The British Scholar Society- Look at the book reviews in each issue (also available 2010-last year in Academic Search database)