If you checked the library or local book store you probably found a multitude of books on the areas that you were interested in. If you skimmed through a few books you probably found they contained many similarities, and some startling differences. You may have found that some books made statements and recommendations that were the opposite of what other books said. Actually there are several reasons for the apparent contradictions. Medical advancements have reversed some traditional thinking.
Some books overemphasize fads that quickly fade away.
Other books are so poorly written that they are hard to read and therefore difficult to understand.