Any books by Horation Alger would be good. He was an American author of the 19th Century who wrote many books for juveniles. They are easier to read and usually have an interesting storyline, though written over 100 years ago. You can find a lot of his works for free on Google Books, Gutenberg, etc. Another author in this class might be RM Ballantyne (the Coral Island is a good book).

Seconding Adam. What kind of books do you like? I could think of a few books, but I'm not sure about difficulty. Can anyone suggest an equivalent reading level? I quite enjoyed 'The Book Thief' by Markus Zusak, which is 5.1 Grade level according to scholastic ... or is that far too hard?

While I am sure those are good literary works (I have not personally read any of them) I think it would be more beneficial for Carlos to read, understand and comprehend a more modern book that is of his interest. :) Carlos - what types of stories do you like?