Who wrote it?
Who Published it?
Verify the author's credentials. Does the author have expertise in the area you are researching?
What else has the author written on this topic? Have you ever see or heard the author's name before?
Has your instructor mentioned this author, or have you read the author's name in another source?
What can you learn about the publisher? Is it a university press? An academic press? What other kinds of books does this publisher publish?