I picked these up at a flea market a couple of weeks ago. The Fantastic Four novel is from 1979, and the Hulk one is dated 1978. Apparently, the Hulk novel is about a nasty-sounding, tentacled monster from outer space. It is intelligent, and on the "preview page" in the front of the book, it tells the Hulk that it will be victorious, to which old Greenskin replies: "Bah! Hulk not afraid of puny jellyfish!"
Sometimes, I really miss the 1970's!