Given the number of gamers in my area who are fascinated by the Celts, the Celtic Pantheon was a very welcome addition to Scion. The rules are clear, the roles (and rivalries) of the various gods and goddesses are well done. The additional Enech rules help make the pantheon unique. Gifts and Geasa are also help make the irish pantheon character fun. And they are not something to take lightly!
As usual in a White Wolf game, substance takes second place to artwork and artsy layout. Book length could have been halved by avoiding massive decorative borders. It could have been made easier to read by sticking with plainer pages.
The technical criticism aside, this book is a "must have" for a scion player who is interested in expanding their game from the basic 6 pantheons. The Celtic pantheon is immensely popular with gamers, and this book will expand your game considerably. My only real complaint, aside from the usual layout issues, is the bok would have benefited from more monsters and creatures from the mythos.
[4 of 5 Stars!]