Princep’s Fury is the fifth book in Jim Butcher’s fantasy series, Codex Alera, and the sequel to Captain’s Fury.
Tavi, now recognized as the princeps (heir apparent to the Crown), has been sent on a diplomatic mission to the distant Canim homeland. There he finds that they have been overrun by the Vord hivemind. Back at home in Alera, the Vord have returned too, killing and enslaving huge numbers of humans. Desperate rearguard actions follow.
Butcher knows how to spin a yarn that moves quickly from one cliffhanger to the next. Grim in places, but it certainly holds the attention.