I often have people contacting me in reference to what UFO books or films they should be checking out. While I do not know every piece of literature on the subject out there, here's a short list of what I feel are some of the best and most credible books or videos on the subject.
BLACK TRIANGLE UFOs
Without hesitation, I call David Marler the premier black triangle researcher and investigator in the world. I highly recommend visiting David Marler's website and purchasing his book. David is a level headed researcher who does not buy into the hype and nonsense too often found in UFOs. David has been most recently featured in an episode of Unidentified and in James Fox's documentary The Phenomenon. The image below will take you to his excellent book and it is a must read.