For my money, that would have to be THE CLONES,
, by P.T. Olemy. I first ran across this paperback trainwreck in 1985, at a flea market; the book itself dates from 1968.
The story, if such it can be called, deals with a mad genius who creates clones with the help of aliens who want to take over Earth....at least, that's what I think
it's about....I've read it five times, and I'm STILL not sure.
The novel reads like a Larry Buccannan flick set to paper-we used to get toasted, and read passages from it out loud. I'm on my third copy of this, as I want to preserve something go achingly BAD.