Reviews are written by critics at or after a the time of a book's publication. They generally try to answer the question "Should I read this book?" They are typically the length of a newspaper article. More in-depth critical analysis usually appears later; critical assessment usually changes and develops over time. Book reviews can also give you a sense of the initial reaction to, and reception of, a book in historical context.
This is a guide to finding contemporary, professional reviews appearing in major newspapers, magazines and journals (including electronic), using library databases, print resources, and websites. It does not cover reader reviews, such as those found in Amazon or Goodreads.
Don't restrict your search to one source. There are significant differences in journal coverage, date ranges, and full-text availability. Notably, periodical coverage prior to 1980 is often not available online. If you need contemporary reviews of older books, you may need to use print or microfilm copies.
Older issues of these print publications containing information about book reviews are kept on the lower level, in the Old Indexes section of the stacks (near the elevator). Newer issues are on the main floor, in the Index Table (by the end of the Reference Stacks).