I expected this to be a rather impartial review of anthropological fringe theories regarding pre-Columbian culture contacts in the New World. Instead, I got Wauchope blasting some of the crazier theorists, most dating back to the 19th century (that bastion of fascinating, but often off-the-wall, pseudoscientific theories and hoaxes). Interesting? Yes. But the author didn't really go into detail on the theories, just ranted about their proponents.
Fascinating? Yes. Convincing? Maybe... The purported presence of Celtic Ogam inscriptions in the U.S. is certainly an enigma, but it would have been nice to have more research besides Fell's own to back up his claims. Also, some of his ideas (like the influence on the American Indian mound builders) seemed to be going a bit too far. The answer, I think, really comes down to whether or not Fell is correctly interpreting his material. Issues with the writing itself: slightly disorganized at some points.
Holzer's book is based around the site of Mystery Hill, NH, which is also mentioned much by Fell. Where Fell is arguing for a Celtic origination, however, Holzer aims for supporting the presence of the Aegean/Mediterranean Sea Peoples. This he does rather ineffectively, since the evidence he presents is hodgepodge, poorly organized, and vague. Much of it is also based on parapsychology, which I'm not sure how to take.