After reading your reply, I realized I have heard of Sorenson as the ghost writer. I decided to look it up and indeed he is often credited as the writer.
I noticed some think it was both of them collaborating, by both I mean Sorenson and Sclesinger, not Sorenson and Kennedy.
I accepted it as it's still the claim of some biographers that he actually wrote it, although like you, I'm skeptical.
I've never read it.