Unlike the Good Prince, which was volume 10 of Fables, the eleventh collection of Bill Willingham and Mark Buckingham's masterpiece, War and Pieces, pretty much demands that you've read the earlier volumes.
It's not that you can't understand what's taking place in this particular graphic novel without having read all that has come before, but you certainly won't appreciate it fully. The storyline has been building toward this huge conclusion for some 75 issues, so much so that Cory Doctorow mistakenly thought that this graphic novel concluded the Fables story.
In fact, there are at least two more collections on the way and I've read bits that suggest the story is perhaps only halfway completed. Willingham is not the sort of author to simply allow his characters a big victory without sifting through the consequences of their struggles.
In any case, in this volume the exiled Fables take the battle directly to the Adversary and his legions in the Homelands. I don't want to say more than that because I shouldn't spoil any surprises. And you can probably find a summary somewhere online if you really want.
I have to say that I've been reading Willingham's material for a while now. I have a nearly complete run of the troubled Elementals comic, which had some fits and starts. I've also got the script book for his Pantheon superhero comic, published in b/w by Lone Star comics. He's always had talent but I found a Elementals to be kind of scattershot in tone and conceptualization, ranging from really intriguing to weird and nearly incomprehensible. It also had a very, very strange collection of characters. Pantheon had some great concepts in it but was let down by poor execution in terms of the production and art. It also tried to cram a bit too much into twelve issues (or thirteen? I forget how many issues there ended up being, as I have the complete story in manuscript form), given all the implied backstory of the various characters and the comic universe that he was revealing. (I almost wish that Buckingham or some other talent like John Cassady could redraw the Pantheon story in color.)
For me, Fables is the real fulfillment of all the storytelling promise that Willingham displayed in those earlier comics. It's not something that I had any interest in reading based solely upon the high concept pitch. But the implementation is a treat. Willingham has found a vehicle whose dimensions are open enough to allow him to stretch even his more bizarre creative muscles, yet confined enough to stay coherent. With this series he really took a leap for me, moving from the ranks of promising journeymen to brilliant creator. And seeing that is as fun for me as reading the wonderful story itself.