I have read alot of books here is a list of my absolute favorite! (some are parts of series so you should read them in order) (just my favorites in the series)
Percy Jackson and the Olympians: -book 1 The Lightning Theif ***** -book 4 The Battle of the Labyrinth *****
The Heros of Olympus: -book 1 The Lost Hero ***** (others still being written
The Kane Chronicles: -book 1 The Red Pyramid ***** -book 2 The Throne of Fire **** (others still being written)
The 39 Clues: -book 1 The Maze of Bones **** -book 4 Beyond the Grave **** -book 6 In Too Deep **** -book 10 Into the Gaunlet *****
The Hunger Games -book 1 The Hunger games ***** -book 2 Catching Fire **** (I am reading book 3 right now)
I also just noticed (like sheppard007 said) no one put percy jackson! shame on you all! it is the best series of aall time ( book 1 and 4 r my faves) u could read Percy Jackson
the Sword of Truth good books, i read only the first three
Why not read the other 7? They get better as they go (Aside from Chainfire, which is VERY confusing, but is intented to be and makes sense at the end of the novel)
Skulduggery Pleasant by Derek Landy! Quite famous in the UK. I've seen the US versions of the book but they fail =/ In the UK there are 5 books in the series.
If you want one with a fairly good amount of thinking involved, I couldn't more strongly recommend The Inferno, by Dante Alighieri. I haven't finished it yet, but I'm fairly close to the end. It is by far one of the best books I've been reading. If you like it, I've heard that the other two books (Purgatorio and Paradiso; it's a trilogy called The Divine Comedy) are rather good as well.
