1979 - Marvel Novel Series #9: The Marvel Superheroes

Marvel Novel Series #9: THE MARVEL SUPERHEROES
Edited by Marv Wolfman & Len Wein
Pocket Books, September 1979
First Printing, $1.95 cover price
Cover by Dave Cockrum

Unfortunately this novel wasn't an actual team-up of all these Marvel heroes, but four stand-alone stories featuring The Hulk, Daredevil, The Avengers, and the X-Men.

Written by Jim Shooter, Len Wein, Mary Jo Duffy, and Kyle Christopher.

1978 - Marvel Comics series from Pocket Books

Here's a list of the Marvel Novel series published in the late 1970s:

1. The Amazing Spider-Man: Mayhem in Manhattan by Len Wein and Marv Wolfman
2. The Incredible Hulk: Stalker from the Stars by Wein, Wolfman and Joseph Silva
3. The Incredible Hulk: Cry of the Beast by Richard S. Meyers
4. Captain America: Holocaust for Hire by Joseph Silva
5. The Fantastic Four: Doomsday by Marv Wolfman
6. The Invincible Iron Man: And Call My Killer...Modok! by William Rotsler
7. Dr. Strange, Master of the Mystic Arts: Nightmare by William Rotsler
8. The Amazing Spider-Man: Crime Campaign by Paul Kupperberg
9. Stan Lee Presents: the Marvel Superheroes edited by Len Wein and Marv Wolfman
10. The Avengers: The Man Who Stole Tomorrow by David Michelinie
11. The Hulk and Spider-Man: Murdermoon by Paul Kupperberg

And here are some covers: