I didn't have any idea what to expect before reading this but did so solely on the basis of a recommendation from someone whose judgement I trusted and I knew nothing about it or the author. But what a pleasant surprise it was.
It was quite a complex narrative structure, with four embedded narratives within the main one, and a big cast of characters that took time for me to get my head around but once I had settled in, this book was a pleasure to read. Gothic prose, macabre similes, a creepy atmosphere and bizarre character and plot developments sustained my interest throughout. The shadowy, intriguing mystery of Malpertius was gradually unveiled but its precise nature only revealed at the end although there were many clues and hints throughout.
In some ways, it felt older than it actually is (published in 1943) and I would recommend this to all fans of classic horror. And I am certainly inclined to read some more of his work if I can find it. Although it will have to be short stories as I believe this is his only novel.