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Check the credentials of the book's author/s. Even if they have a PhD., check to make sure they have a degree in the subject they are writing about. Books usually have an "about the author" section, but you may still need to look the author up on the internet to learn whether on not they are a good authority on the subject matter.
Step 2) Check the documentation.
Good quality academic books will have a full reference section. Check these references to make sure that they are expert sources of relevant information. For example, academic books will usually cite other academic books and publications, not random websites.
Step 3) Check for bias and objectivity.
It is not unusual for an author to have a certain bias toward theories or opinions. It is important that you determine what that bias is, however, in order to evaluate the information and use it to back up your own arguments.
Step 4) Check for the intended audience.
Books are written to appeal to different groups of people. Is your book considered popular science and written for the lay person, or a technical book meant for fellow experts in the field? Is it meant to introduce the topic to beginners or for a more advanced audience? The intended audience for the book should be roughly the same as for your paper or you will need to provide further explanation for why you included it.
Step 5) Check for currency.
Always check to see when the book was published. Some books are always relevant, but others will go out of date. If it's a text book, check to see if there is a newer edition.
Step 6) Check for relevance.
Simply put, does this particular book fit your needs? It may not have the exact information that you want. You also need to check whether or not you need a primary or secondary source. A primary source is an original source of work. A secondary source discusses primary sources. For example, a play by Shakespeare, even if it is an edited copy, is a primary source. A book that discusses the play and analyses it, however, is a secondary source.