George R R Martin springs immediately to mind. The current ruling family usurped the last one in an armed rebellion because they were batshit crazy. Then one of the kingdoms secedes because the new lot are also fairly horrible. I mean, it's Song of Ice and Fire, there's rebellion and crazy rulers and pretenders all over the place, but it definitely deals with that. And with the ambivalence the populace has to the idea. (Jaime is still 'Kingslayer' and criticised for breaking his oath to a king that wanted to burn people alive and whom everyone agrees they are better without. It's complicated.) I have many issues with ASOIAF but that's a thing it does very well.

It does seem like I've read another one somewhere, but can't think of what it is off the top of my head.