The book traces the history of beliefs in hollow earths up until today when various contradictory ideas about UFOs and Hitlerian refuges continue to proliferate. The reviewer's final comments say a lot about why ideas such as these, as well as others that have no evidence or basis in reality (astrology, psychics, homeopathy - need EoR go on?) persist:
That such notions have proved so enduring should not surprise us. Their appeal is the same as it has always been, the dream of a world which is richer and stranger than our own, the hope that we are only ever a few metres away from the fantastic, the belief that there are secrets kept from us which, if uncovered, would make sense of life. It is to this spirit of daft optimism that Hollow Earth pays tribute.
Which, of course, still doesn't make any of it true.