Beside the book of Katok and Hasselblatt, mentioned above, i would recommend Dynamics in One Complex Variable of John Milnor (if your are interested in holomorpic dynamics) and the book Dimension Theory in Dynamical Systems: Contemporary Views and Applications of Yakov Pesin (if your are inetersted in dimensional theoretical aspect of dynamics). More from a physical view point we have the chaos book http://chaosbook.org/ for free. I wish You to have much fun with math.