I'm at work, and only have a little bit of spare time, but the book contains:
- new spells (many) and sorcery styles (cosmic sorcery and immortality)
- new feats relating to sorcery, or for sorcerous beings, and a few which could be used by non-spellcasters (Awesome Blow, Craftsman, Noble Blood, etc.)
- permanent sorcery rules, including the creation of new dreadful and amazing forms of life
- magic item construction rules
- a listing of famous magic books and magic artifacts
- silver weapons
- more sorcerous paraphrenalia, such as drugs, potions, alchemical items, etc.
- creatures and monsters, animated objects, templates (Child of Jhebbal Sag, Salome), demons, demon lords, etc.
- sorcerous cults
- sorcerous prestige classes (Lord of the Black Ring, Master of the Black Circle, Sorcerer of the Scarlet Circle)
- stats for Atali (and her brothers), Hadrathus, the Master of Yimsha, Natohk, Thoth-Amon, Tsotha-Lanti, Xaltotun, and the mummy of Ahriman.
- it is capped off with a longish section on GMing magic in the Hyborian world, and how players might best use it to achieve the proper flavor.
Plus, a higher boobies/page rate than the core rulebook (meeting my "more pornography" requirement)!
As for editing, it looks pretty slick, but this is a first pass glance-through. I haven't had the time to read it with any thoroughness.