1: The hunger games series http://www.thehungergames.co.uk/
The hunger games is a gory tale of a future USA with action, danger, love, and rebellion.
2: The Percy Jackson series http://percyjacksonbooks.com/
With 5 books in the original series this is a long series that will engage the reader in the utmost extent.
3: Harry Potter series http://harrypotter.scholastic.com/
This super long and very popular series is a great suggestion for any middle schooler that likes fantasy.
4: The Eragon series http://www.alagaesia.com/
This Four book cycle is incredibly popular. With a relatively high level of vocabulary, this book takes a higher level reader to continue to be interested in the content.
5: The Diary of a wimpy kid series http://www.wimpykid.com/
I personally have never read these but I hear that it is a fairly popular comic book. It is a lower level reading for middle school use but is a good choice for a quick read.