I wrote a
review of the first book
as a pdf.
There are three
[cite]. The first is kind of like a player's handbook with a little extra on the setting, I think it's enough for a full game. I haven't read the other two, they certainly do look useful. More info on the setting and campaign ideas are always nice.
Mechanically, the game is a fairly standard OGL clone, poorly written at places, and I suspect not well balanced. It has some original ideas, like the classes being racial classes (kind of like a monster's HD), random mutations, and Sin Ratings (a la Challenge Ratings). I believe playing out with it will reveal some wonky elements, like Sorcerers being too powerful or whatnot. The first book, by itself, is sufficient but there are some parts that are still missing (like the Lost Souls game stats, and being able to play one).
The world itself I found very interesting. It's heavily inspired by Dante, but it's definitely not simply Hell. There are lots of factions, political camps, and so on. I didn't like the prevalence of modernish technology, but this IS a big part of the game, a reshifting of the power balance that kind of drives the setting to some extent, creating tension and power vaccums the players can step into.
I never played Infernum, but despite my suspicions of its mechanics I'd like to give it a try someday. I certainly agree it isn't talked about as much as I think it merits.