As with any source, the quality and relevance of information in books needs to be evaluated. What to look for:

Authority of the authors, editors - Determine the expertise of the authors, does it match the subject content of their writing?

Scope of Content - Does the content cover your topic to the degree you need? Is it in-depth or does it simply provide an overview with little facts, details, analysis?

Timeliness - Is the content timely for your topic. This is determined somewhat by the time period of your topic.