Searching Tripod for "reader's guide" plus relevant keywords for your topic may turn up additional guides, but we do have some "reader's guide" book series:
Tripod searches for individual journal articles as well as the Tri-College libraries’ collection of books, journal titles, multimedia materials, databases and more.
Limit to "Book Reviews" to find scholarly reviews of a title. This is a citations/abstracts database, but click the FindIt button on a record to check for full-text access.
JSTOR is one of our major multidisciplinary full-text journal databases. In the advanced search, limit to "Reviews" to find scholarly book reviews for philosophy, political science and many other disciplines.
Google Scholar will have a lot of overlap with Tripod Books and Articles searches. It has less ability to filter out lower quality results and to execute complicated searches, but is still very useful for finding the greatest number of sources.