As you search the library catalog for books, you will find lots of ebooks (see below). Click on the button to access the book online.
For help using ebooks, refer to the library's getting started guide to reading, downloading, and using ebooks.
America: History and Life includes citations to book reviews from over one hundred key journals in the area of U.S. history, 1954-present.
H-Net Reviews is a good online source for scholarly reviews; limit by publishing list (for example H-USA or H-US1918-45) to narrow the results to US history.
JSTOR includes archived issues of academic journals, allows the searcher to limit to book reviews only.
Project Muse covers the arts and humanities and social sciences. From the article search screen, you can limit to "reviews only."