Drug War Heresies, MacCoun & Reuter, 2001, ISBN: 0-521-79997-X; This is the best recent overview of drug policy. It's written from a conservative point of view (small 'c').
The Theory of Democratic Elitism: A Critique, by Peter Bachrach, 1969, 1980, ISBN: 0819111856; This is an excellent short book on politics which will give the reader a good overview of how modern politicians and neocons think and act. Such a book will help you get your head around the paradoxes of the War on Druggies.
Informing America's Policy on Illegal Drugs: What We Don't Know Keeps Hurting Us (2001). Another quality free e-Book, by National Academies of Science, 2001, ISBN: 0-309-07273-5. This is available in open-book format, allowing it to be read on-line! You can also order the paper version for a more convenient read.