Werewolves (?) with prohibited cannibalism

[u/Moist-Permission2643]

I'm looking for a fantasy novel I read in Czech around the early 2010s (likely translated from English, but not certain).

It wasn't a typical werewolf novel. It featured an entire race/society of wolf-shifters who lived as humans most of the time but could transform. One of their greatest laws was that cannibalism of another wolf-shifter was absolutely forbidden. Anyone who did it became a permanently corrupted outcast. They remained intelligent and human-looking, but became pale, gaunt, lost the ability to transform, and were looked down upon by the rest of society. They often served other wolf-shifters.

The protagonist already had one of these outcasts as a servant before he himself became one. Later, his wife was manipulated by an evil force (possibly another wolf-shifter) and unknowingly served him soup/stew made from their own child, causing him to unknowingly commit cannibalism and suffer the same fate. Does anyone recognize this book?