This is an interesting collection of stories from real people who have claimed to have visited the interior of the Earth and interacted with the inhabitants. Many are based on folk tales and legends, but it covers people right up through modern times. A lot of emphasis is given to the legendary Shaver Mystery (including a nice, but somewhat out-of-place history of pulp magazines) and the rather dicey work of Raymond Bernard, the writer of the Hollow Earth treatise.
The book’s padded out with promos for the author’s other books, and another out-of-place article, this time on “found manuscripts”. It’s an intriguing read though, especially if you’re a fan of this once popular genre of science fiction.