Well, I love YA, so here xD

1. [color=6ecff6][b][i]The Hunger Games Trilogy~[/i][/b][/color] Susan Collins
2. [color=6ecff6][b][i]The Harry Potter Series~[/i][/b][/color] J.K. Rowling (See where this was already mentioned, but heck with it.)
3.[color=6ecff6][b][i]The Mortal Instrument Series~[/i][/b][/color] Cassandra Clare
4. [color=6ecff6][b][i]Percy Jackson and the Olympians Series/The Hero's of Olympus Series~[/i][/b][/color] Rick Riordan (The second series is a follow up with the first.) 
5. [color=6ecff6][b][i]The Divergent Series~[/i][/b][/color] Veronica Roth