Horseman of Vangal is in the same book that Silver Knight, the revised Incarnate (which you can also find online), and the Coursean of Idra are in. Secrets and Societies. Also the write up on the group is decent. It's a good book, but a little short for my taste.
Two books I definately recommend, Hollowfaust and Calastia. Hollowfaust, for some of the spells, magic items and general goodies. (Plus it's a great city!
At least I think so.) Calastia, I recommend more for foes or if you want some interesting NPCs.
Vigil Watch: Warrens of the Ratmen is also another one I recommend, but I will warn you, the ELCs for the Slitheren in there, are off. At least for some of them, they are.
If you need a good adventure, try the Serpent Amphora Cycle. Certainly will be VERY challenging to parties at the recommended levels.
I also think if you have CC 1, get Creature Collection Revised. Believe me, you'll be glad you did. Templates for some of the creatures from CC1, (such as Hags, Unhallowed and Morgaunts), fixed stats, plus three apendixes, one for the racial stats for the races of Scarn/Scarred lands (including those from the Termana Gaz like gnome, terali and gnoll), and one for how the MM monsters fit into the Scarred Lands. This book won't be out until the 20th of January.
Also I would say, if you liked some of the feats from R&R2, pick up the Player's Guide to Wizards, Bards and Sorcerers coming out in Feburary.
