Understanding Molecular Simulation, Second Edition: From Algorithms to Applications (Computational Science) by Daan Frenkel Berend Smit (2001-01-01) Paperback
A great, comprehensive guide to the world of simulations. Clear, precise and going from the basics, this is an excellent textbook for beginners. I particularly like that it lays good mathematical and physical foundations of the methods and tricks used in simulations, so that the user isn't put in the situation where he/she feeds data into a black box and expects output. (Granted, I read thoroughly only the parts concerning molecular dynamics, but I also liked what little I read on Monte Carlo.)
It is a comprehensive guide on molecular dynamics and Monte Carlo simulations. This book is oriented more on physicists and material scientists than chemists. Despite of difficult maths, the concepts are easily understood, although sometimes the author chooses not the easiest way to introduce certain approach. Algorithms written in pseudo-code greatly simplify understanding. Being a chemist, I also think that a chapter on different kinds of force fields would be appropriate.