The central story of Witches has the rise of Baba Yaga as an enemy of the Fables, courageously opposed by the winged monkey Bufkin and his allies; and also a parallel story line of shifts of power among the Fables who are now at their farm, exiled from New York. The former worked better for me, the latter still needing resolution in a future volume.
The first pages of the book, however, are a rather effective vignette of a group we have not encountered before called the Boxers - a fighting order who trap their enemies in large magical boxes; it's Willingham's riff on any number of young warrior stories, but done rather well. And the last pages take us back to the former Frog Prince's new kingdom of Haven, with a parable about peacebuilding in a post-conflict society; I'm sufficiently familiar with these issues from my work that I found it a little didactic, but perhaps that won't be the general reaction, and some of the character moments were rather memorable.