1st) Why only 4 stars? It ended. While it has a high page count, many are wasted with useful information and not describing the setting. The setting is plenty detailed. If you buy it, you will understand.
2nd) It was worth every cent of $15; but, for gamers on a budget, it is a little pricey. If you can afford it, it is some of the most interesting work done in gaming.
3rd) Which rules? LotFP is a retro clone. The art is amazing and the flavor unbelievable. This module/campaign would play out in many game systems. I hate to say "better"; but I will. The grit of Warhammer 1st or 2nd could really work. Oddly, First Fable came to mind first. Maybe for kids, probably not.
AR&PL reminded me of the Ravenloft setting. It could easily fit in as a realm there; although it would be the cool one. It also could fit as "behind the hedge" for Changeling or the other White Wolf games.
Bottom line, it is genius.
[4 of 5 Stars!]