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)
America: History & Life database contains book reviews written since 1964
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.