This volume reprints four of the top 100 Marvel comic books ever, as voted on by fans. They are all great issues; the only problem is that some of them are part of multi-issue arcs, so you don't get the full story in one volume. Still, these are some of the best and most important comic book issues ever, and are definitely worth reading for any Marvel fan.
Issues in this volume (and their importance):
9. Ultimate Spider-Man #1 - First issue
8. X-Men (vol. 1) #1 First appearance of the X-Men and Magneto
7. The Avengers (vol. 1) #4 First (real) Captain America appearance since World War II
6. The Amazing Spider-Man (vol. 1) #121 The death of Gwen Stacy