Beyond the strategies of looking for the book's title in Amazon, Google, or even Wikipedia. You can leverage the library's subscriptions for a more comprehensive search for already existing books reviews.
Note: when searching in Amazon, you might want to use the ISBN number to find a specific edition of a book, or include the author's name if the title is fairly non-descript. These strategies also apply to Google, with the added caveat that in Google you may want to put the title in quotes, and include the phrase "book reviews" for more effective searching.
When you look up a book in Amazon, you can look at the related titles listings on the page, but there are library resources to help develop a more extensive list of titles.
Libraries use Library of Congress Subject Headings to categorize titles, and help researchers easily find related titles. Often a title will have multiple subject headings to illustrate the multiple topics related to a book. These subjects can be found in the catalog record for the book.
There is actually a method behind our madness. The libraries use the Library of Congress Classification System to make sure that books with similar topics are organized together. So, when you locate a book on the shelf, look to see what books are on the neighboring shelves. They are usually ones that deal with the same or similar topics.