Elwyn R. Berlekamp, John H. Conway and Richard K. Guy,
Winning Ways for your Mathematical Plays, Academic Press, two volumes, 1982.
Second edition: AK Peters, four volumes, 2001-2004.
D.P. Williamson and D.B. Shmoys,
The design of approximation algorithms, Cambridge University Press, 2011
Amy N. Langville & Carl D. Meyer,
Who's #1?
The Science of Rating and Ranking,
Princeton University Press, 2012
T.H. Cormen, C.E. Leiserson, R.L. Rivest and C. Stein,
Introduction to Algorithms (3rd ed.), 2009, MIT Press and McGraw-Hill
And even older: 2008: DNA String Algorithms; 2006: Artificial Intelligence and Complexity (JMdG&WAK); 2004: Computational Molecular Biology (HJH); 2003: Computational Molecular Biology (HJH); 2002: Advanced BioComputing; 1993, 1994, 1995, 1996: Geavanceerde Algoritmen (JMdG&WAK).