I have a soft spot for this book, but it has not held up so well over the years. Perhaps the issue is more that society and the hobby have moved on. There's still a lot to like, and this game would benefit greatly from a 20th anniversary edition to clean up the warts.
Honestly, the largest problem is the general disrespect it has for the source material it draws from. While I would never go after it for imperfectly fitting any particular angelology, but basically ignoring all of them and naming the seven Houses of the Fallen after gods and sacred/mythic animals from various ancient traditions is not great. Plus, the Hebrew was horrific, to the point of being mildly offensive, calling the angels "elohim" as though that was a plural term and not in active use in a real world minority religion (especially given that "malakim" is a perfectly good word for them, and is used in a specific angelic name in the book, most of which are also terrible). Oh, and of course, it does include an offhand remark that "severely autistic people" are less fully human. That...needs to be excised.
However, when viewing it as a Milton-esque exercise it succeeds quite well when you get past those trappings. The Factions are all logical responses to the trauma of the rebellion and time in hell, and it combines themes from Vampire, Mage and Changeling in generally creative ways. The mechanics are solid and will need minimal updating for compatibility with 20th anniversary rules.
But the cultural insensitivity issues and the lack of research into the mythology that they're building on are sticking points. If the book were being written today, more research, more care with languages, better choice of proper nouns (even just using names for demons from different traditions instead of just gods, like calling one House Sheydim would not bother me, as an example) and of course, not putting "severely autistic" people into the same category as people who are comatose, braindead, and who've had their souls snuffed out.
So, a good game, but running it in a way that avoids these problems would take significant work.
[3 of 5 Stars!]