In some ways this is the most amazing novel I have ever encountered. Its imaginative range, its gorgeous language, and its mesmeric power lift it far above almost anything else. Some of the characters and images - Geard, the mayor and founder of a new religion; Evans, the tortured antiquary; the haunting vision of the Grail-Aquarium; and the invisible naturalists studying the town's population all come to mind - are unforgettably original. The book is by turns sinister, astonishing, mystical and comic. Think of a kind of Dickens meets Hardy meets Lawrence meets Blake, and you'll have some idea of what to expect.
The last two names point also, unfortunately, to the book's flaws. Like Lawrence, Powys can be embarrassingly gushing, and like Blake he can bore or bewilder when he isn't firing on all cylinders. His mystical flights occasionally spill over into bathos! and his style moves from the sublime to the downright infuriating! In particular, I really wish he had vowed never to use another exclamation mark before beginning this book! More broadly, the text is very long indeed and needs some determination in places.
But these are trivial complaints. Powys is a truly unique writer in the whole history of English literature, and his intricate, minutely-detailed yet cosmic vision is one you'll never forget. Not light reading, but the rewards along the way dwarf those of most other twentieth-century works.