I thought this book was quite solid, fleshing out the influence rules from the core Chronicles of Darkness book in an easy to understand and evocative way.
The best parts of the book were the sections on general guidelines for influence use and the example influences. Those were worth the price of the book alone. I think the core rulebook for Chronicles would have been improved with a version of the general guidelines included here. The examples for influences are nice and varied and should be able to accomidate a wide variety of spirits and ghosts in a game.
The last section on Merits and Powers wasn't bad, but it was shorter than I was hoping for. That said, the author directly references already existing merits and powers for the various supernatural groups in other books that can be used for further influence control, which I thought was a particularly nice touch.
By my count there is:
One Mortal merit
One Vampire Discipline (five ranks)
One Werewolf Rite, One Werewolf Gift (That can be used in five different ways)
One mage Spell (With three variations)
All that said, the entire book is 43 pages, so it isn't light on content by any means. It just left me wanting more in the final section.
As far as some final thoughts:
The layout is clear and easy to follow
The art is good and fits the content
The mechanical powers seem largely balanced and evocative
I would recommend Ephemeral Influence for anyone wanting to use Spirits or Ghosts in their Chronicles of Darkness game.