I really like the writing of Scott Westerfeld. He makes his characters, especially his female protagonists, smart, charming, and witty, and then fills them with just enough angst, waffling and unsure of themselves-ness to be believable teenagers.
In the young adult category, check out the "Uglies" series - the trilogy of "Uglies", "Pretties", "Specials" as well as "Extras" which is the same world but different characters.
And, in the steam-punk category, he's got a series starting with "Leviathian" which reimagines the beginnings of WWI in a steam-punk landscape. Which turns out to be very interesting for adult readers (or those who know a little about the real WWI) - an archduke is murdered, alliances between countries require support in the event of war, Turkey is waiting in the wings - much more interesting than a history textbook!
I also liked the first "Maze Runner" book by James Dashner. However, the second went downhill and the third was completely unsatisfying - the author used the "wave the magic wand" method of resolving the plot that had been evolving through the three books.