Never have I seen an author sell their own work short as I have in this book. The cutsey last paragraph, in which the author mocks True Believers (OK, most of them deserve mocking), misses the big ideas that he had been exploring for the previous 300 pages.
People need a frontier on which to pin their hopes for a better world. The frontier is distant, but it is always attainable to those who are determined. Whether the Hollow Earth represents a new Manifest Destiny, as it did to Symmes in the 19th century, or a utopia, as it did to the Koreshite movement, or simply an escape from a miserable life, as it did to Edgar Rice Burroughs, countless people have seen in the earth what they have most wanted to see.
Else what's a heaven for?