I admit it: I'm a sucker for Redwall books. I've read all of them; when my Library ordered The Sable Quean, I was the first to place a request for it.
Of Jacques' most recent Redwall books, High Rhulain was the most disappointing, though Eulalia and Doomwyte were better -- but this one! The Sable Quean is, in my opinion, the best Jacques book to come out since Triss. (Taggerung is my all-time favorite, for those dying to know.)
Alright, I'll try to keep this spoiler-free:
The plot has a number of familiar Jacques elements, but he keeps you guessing here more than I might have anticipated. Memorable villains (if not the most ostentatiously evil) and an ensemble of sympathetically displayed woodlanders give the novel an excellent cast. I feel that Jacques should have focused more on his hero rather than on his hero's comical friend, but that is a minor quibble. This novel does not have the epic feel of Mossflower or The Long Patrol, but tends to convey even more than usual the folksy atmosphere of Jacques' world.
I can recommend this entry in the Redwall cannon with great enthusiasm. Check out your library and start reading. I did, and it only took me less than a week to finish, college work aside (yes, I still read Redwall books at 19). Happy reading!