In addition to finding reviews in databases such as Academic Search Premier, America: History and Life, and JSTOR, we have these print indexes to book reviews:
Book Review Digest - Reference Z1219.B72
H. W. Wilson Company 1905 - Contains references to book reviews in popular magazines and book trade periodicals such as Publishers Weekly, including a note about the length of the review and brief excerpts.
Book Review Index - Reference Z1035 .A1 B7
Gale Research Company 1965 - Indexes book reviews for some 50,000 books annually appearing in around 450 popular and scholarly publications. It covers more scholarly books than those indexed in Book Review Digest, but does not provide any excerpts from reviews. Search by title or author.
Combined Retrospective Index to Book Reviews in Scholarly Journals, 1886 - 1974 - Reference Z1035 .A1 C6
Carrollton Press 1979 An author and title index to reviews published in the complete runs of 459 scholarly journals. Because of its focus, it doesn't overlap the Book Review Digest, but covers more specialized journals.