Kurson's book seems to be more valid and does not have an ax to grind. Not too interested in what Kurosn wrote before because his book stands or falls on its own merit.
If you title a book that claims to descredit another book on the same subject, you expect it to be filled with facts and positively show how the previous book was inaccurate. That is not the case, it seems. By just giving a possible alternative to the original story amounts to just that, A POSSIBLE ALTERNATIVE. If you claim to EXPOSE then you must fullfil that goal and Gentile seems to be short, way short, of that goal.