One of the things a lot of people have had trouble with in Chronicles is the Influence system. While assorted books get into the basics of what dot of an Influence can do, they're meant to be mostly plot devices. This doesn't help some of the more mechanically-minded storytellers, or players (as PCs are capable of getting Influences).
Ephemeral Influence breaks down the mechanics, still leaving some open to plot device but giving you a sturdy framework to build off of. It starts with breaking down each dot, similar to how Mage has its Practices, it offers you some rules capable at each dot of Influence. Then it goes into specific Influences, covering Air, Authority, Death, Dogs, Disease, Earth, Electricity, Emotions, Fear, Fire, Information, Location, Time, Vice, and Water. Each Influence has many individual powers beneath it, offering rules and Tilt suggestions for them, including multiple options at different dot levels. There's a wide variety of powers here, and they're under suitably generic Influences that a ST should be able to convert them for more specific needs (Air to Smoke, Water and Earth to Mud, Water to Blood, Dog to basically any other animal). Each Influence has between 13 and 15 powers.
And while that makes up the bulk of the book, that isn't it. The last chapter offers ideas and mechanics for how some other gamelines can gain Influences (the Mortal section references some other books, mostly fanmade: Hurt Locker, Borrowed Power, and Second Sight: Third Eye, though it offers mechanics of its own). For Vampire there's an update to Blood Tenebrous, the spirit-affecting Discipline from first edition's Book of Spirits. There's a new Rite and Emotion Gift for Werewolves (that offers for the most part Influences over emotions). A spell for Mage that allows for a sort of 'reverse claiming' allowing mages to put spirits and their abilities at the disposal of another. All use the second edition rules.
It's a pretty good book. If you've ever had issues with figuring out mechanics for Influence, I can't recommend it more.
The only complaint I have is pretty minor, in that the Honor Facet of the Gift should probably allow for targeting packmates, given the Essence cost. And Dalu is misspelled.