Papers Books in general are not sources of basic research data. Books are second or third hand accounts of research, biased and filtered by having passed through the writer's head.
Books are collections of anecdotes.
Books are descriptions of the world the way the writer would like it to be, the way someone thinks they remember it, or the way someone has dreamed it, rather than the way the world really is. Newspapers and magazines are much less reliable. The World Wide Web is even less reliable. Information to be accorded a modicum of reliability is quantitative information published in technical journals where the articles have been referreed and reviewed by other experts in the field before they make it into print. Such information may also be wrong, but it is the best we have.