Newspapers can provide you with valuable information. They include book reviews, author interviews, etc. Historical Newspapers can also provide you with information on how the book was received when it was published, if it was published within the paper's date range.
Helpful information, including examples, can be found on the Purdue OWL MLA Formating and Style Guide (8th ed.)
Additional information about the 8th edition of the MLA Style Handbook can be found in the MLA Style Center, including A Quick Guide to Works Cited, What's New and Ask the MLA (For example, you can find the answer to "How do I cite an image reproduced in a book?")