I read the book more than 10 years ago.
It's about a detective, set in a futuristic setting where humans have developed the ability to genetically alter their body. I remember that the book would talk of bird humans, and there was a somewhat main character that was altered to be like a gorgon (or Medusa), she flirted with the detective or something.
I remember there were a lot of murders happening, and I think it was mainly murders of the altered humans. There may have been separate groups of them, as I think a few of them was wrapped up in crime syndicates or something.
Other details I can remember is it was sold at Dollar Tree, and had a gun on the cover and I think a flower (maybe). The title was two or three words I think.
I've seen some questions similar to this one, and it is not Orphan Black.