Luna was always a mysterious figure, with much less known about her than the Unconquered Sun. John Morke has done a fabulous job of creating an identity for Luna and giving her a history, in a way that both fits her previous sparse portrayals and expands on her in ways that give plenty of ideas for Exalted players. In addition, he's also created some tantalizing hints about Gaia and why it may someday be possible to play Dragon-Blooded in Space.
Speaking of space, there's also a section on the moon and what you can do there.
Holden Schearer has also thrown in a bunch of outstanding new Charms, giving Lunars the spidey-man powers they've always wanted, along with some really delightful expansions to Secure Den Prana, just in case you wanted to build Narnia in your closet. In the back, there are new martial arts, including the long-demanded White Reaper Style, the signature martial art of Lunar elder Lilith and the ultimate army-killing style.
The new Luna is a fantastic animal, a veritable deity very suitable as a patron of the Stewards. Highly recommended.