Book reviews give you an idea of how a book was initially critically received.  Sometimes initial book reviews can be differ dramatically from later critical analysis.

Book review sources: 

• Book review digest -- for more popular works
• Book review index -- contains reviews of scholarly works -- Index/Abstracts area, main floor.
• Project Muse  -- good source for reviews of scholarly books in the humanities.
• Wilson Omnifile -- select 'book reviews'  from the document type dropdown choice box.
• Book review guide -- links to many print and online sources.