Vril; the Power of the Coming Race: Now Available!
This interesting piece of science fiction literature from the middle of the 19th century is a bizarre fusion of modernism and sword-and-sorcery fantasy. Akin to any comparable Atlantis-and-Agartha style work, it's written well enough to be entertaining, and is actually a very good fiction read; but its importance, for occultism, is far greater than its fictional impact.
The author himself was assuredly connected to the spiritual- Blavatsky apparently was familiar with this work, and like other utopian novels it went on to directly inform the spiritualism and new agery of the next half century. This is not surprising, Bulwer-Lytton's various works also influenced the rise of Victorian gothic works. For those into subterranean fiction, it's a must-read. For those interested in the works that influenced 20th century occultism, even more so.