The Host question

Well with the Host's premise all I can think about is Invasion of the Body Snatchers and Stargate cause of what the parasites looked like and how they attached to the brainstem.
Host really didn't have the most original concept but it was an alright book.

Never read the books you mentioned, but I thought this was very similar to the Animorph series. The main antagonist in that series was a slug-like alien that goes into human brains and turns them into zombies basically. Once I got further into The Host the story def. went another direction than any of the Animorph books did but I still thought the set up was almost too familiar.