Like some other fish they have a strip of red meat that should be removed. They should be skinned rather than scaling because it's easier. Beyond that you can fry them like any other fish that has a lot of bones, cut slits to the backbone every 1/8", make sure you get flour in the cuts and fry them up crisp.
As far as taste goes, there's a successful restaurant in Omaha that specializes in carp. My great aunt used to bake them if they were about 12# or bigger and as I recall the bones, while plentiful, were too big to be dangerous.