Approximation Algorithms http://link.springer.com/book/10.1007/978-3-662-04565-7
How to Solve It: Modern Heuristics http://link.springer.com/book/10.1007/978-3-662-07807-5
Modern Graph Theory http://link.springer.com/book/10.1007/978-1-4612-0619-4
Computational Geometry http://link.springer.com/book/10.1007/978-3-662-03427-9
Modern Heuristics is in my top-k books of all time. Check out Zbigniew Michalewicz's other books @ http://cs.adelaide.edu.au/~zbyszek/books.html
thank you ! this led me to his books on evolution programs (Genetic Algorithms + Data Structures = Evolutionary Programs), which is an excellent book as well.