Werewolf the Forsaken, the second core setting game for new World of Darkness is perhaps one of the best roleplaying games published TO DATE! It's just flexible - you can run a generational game in a small valley, or remake Wolfen, or delve into ancestral blood curses similar to Ginger Snaps, or just play it for the combat fun. Instead of cleaving narrowly to a particular adventure type, it offers room for expansion - it feels together. Predators expands it a little further, detailing spirits and going into more detail about the Ridden.
The core Werewolf rule book went into some detail about the spirit world and what it was like, but it not fully developed - but this supplement expands it like no other.
Predators essentially lays out exactly what spirits are like, broken down by category - mechanical tool-spirits, god-like spirits, animal-spirits, plant-spirits and so on. Instead of describing spirits in vague terms, the book goes into specific, concrete detail about what a spirit's like - where it typically spawns, what they look like and how the storyteller (or game moderator) can use them in a game.
It's worth noting that the book covers the entire range of spirits, from high to low - besides natural and artificial spirits, we also get the Celestial spirits (sun and moon, including lunes), conceptual spirits (apathy, war, dreams) and the bastard hybrid Magath. The Magath get some nice writeups, including a dump-truck/pain spirit who wanders the spirit highways, destroying car-spirits to siphon off their pain, and a dog/information spirit that haunts a library.
We also get to find out how high tec data/technology-spirits work, and how book and computer spirits prey upon them. We also get stats for Ghost Children, the spirit-spawn of two werewolves, who have some pretty nasty stats and a ban that demands that they must revenge themselves upon their parents. The chapter also includes some new spirit-powers, ranging from the generic but useful (Mechanical Possession, Speed, Emotional Aura, Telekinesis) to the specific (Dessicate, Fearstruck, Final Strike, Clasping).
There is also an entire chapter dedicated to the Ridden - spirits who jump into people's bodies and 'ride' them around. The Ridden can fill just about any need in a horror game, ranging from Lovecraftian Innsmouth folk (possessed by fish spirits) to cannibal hillbillies (gluttony spirits) to animals that are too smart for their own good (possessed by a spirit of their own species) to Swamp Thing (plant spirit in a human body) to any shapeshifter that you want as a villain.
This book represents everything that the New World of Darkness, and Werewolf the Forsaken are all about: the took-kit and rules to create a new race without having to create a splatbook, the ability to use what you've already been given rather than having to buy something new. The possibilities are limitless. This book is one of the most essential and valuable books to the Werewolf the Forsaken game line.