I just finished reading this book last night, and I really do not know what to make of it, short of "This is a piece of work whose importance cannot be understated".
First and foremost, I believe I should comment on the content, which for it's time, had to have been the most depraved and psychotic thing put forth. It still is shocking in the modern age, and I now understand why sadism took its name from de Sade.
That said, I believe on some deeper level, the book is much more important. Here, de Sade manages to create a place where the morality of man is completely irrelevant, a place where power and dominance are glorified and are the order of the day. The portrayal is chilling, but perhaps this is because it so starkly contrasts with our current egalitarian world.
All in all, I would recommend this to a select few, people I think would be able to look past the imagery in order to appreciate the truly beautiful deeper philosophical concepts behind it. With this in mind, it is highly recommended to Satanists.