There are several places to find book reviews, here are a few suggestions-
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.
Combined retrospective index to book reviews in scholarly journals, 1886-1974
Combined retrospective index set to journals in history, 1838-1974
Reviews for over 1.5 million English-language adult and juvenile fiction & non-fiction books. Reviews are from popular magazines, newspapers, academic journals, and library review media. 1908-1982.