The Marvel Adventures books (Avengers, Spider-Man, Iron Man, Hulk, Fantastic Four, and Super-Heroes) come collected in handy four-issue digests (or sometimes three issues and an annual). You can find them for cheap on Amazon.com, and most of them are even part of this 4-for-3 promotion, buy four and the cheapest one is free.
I should note that these books aren't quite part of a continuous universe. Frex, in one of these pages Spider-Man (who's an adult here) says he's never heard of Hawkeye. Yet in his book, he (as a teenager) teamed up with Hawkeye against Frankenstein (really) and had heard of previously.