As for the comment that 'evidence isn't found in a book' which someone else made, that isn't strictly true.  Dickens' novels are used as part of the evidence about what Victorian England was like.  Not exclusively, but in part.  Likewise, with the Bible; there are other sources of evidence such as archaeology but the Bible is a useful resource. 

Evidence may be written/recorded about in a book or witness statement or texts  Andy - but the evidence is usually taken/observed from another source.