This was one of those books that were laying around and I fancied seeing what it was like. The book is of a similar format to many of the "Unknown" and "Mystery" books of the late 70s and early 80s. In fact several of the entries I am sure I have seen elsewhere in other books as well. The articles is fun to read if very dated (modern surveillance for example would have no doubt had a lot to say about some of the "sightings" for example) however like most of these books all they can offer are opinions, ideas and conjecture since as the title says (and at the time it was published) no one can explain them.