I don't have lots to go on as I read it about 5 years ago.
Male author
Set in an alternative world (but more fantasy than scifi)
People live in a walled city and are governed by a council
The council are almost all at each others throats
Someone discovers a way to travel by using a stone or similar to stand on
Someone experiments with crossing humans with other species
It's part of a trilogy
It's a bit like Mervin Peakes Gormenghast stories
The cover had a black and white drawing of the city on it, at least, I'm sure the edition I read did
It's driving me mad trying to remember.
I put myself into the hands of MN and the collective wisdom here.