The book - as the title implies - featured team-ups between different superheroes who otherwise might not normally work together in their own respective books (if they had any, which many did not).
The great majority of the title's issues featured Spider-Man teaming up with other characters, ranging from the unlikely (Frankenstein's monster) to the downright ridiculous (the Not Ready For Prime Time Players, e.g. Jim Belushi, Dan Aykroyd, and others of the original Saturday Night Live cast). Most of the team-ups were more straightforward superhero adventurism, though the rotating cast did tend to make for spotty continuity.
Occasionally the Human Torch got the spotlight, as he occasionally teamed up with other heroes such as the Hulk (#18), Iceman (#23), Thor (#26), and Iron Man (#29).