An Introduction to Stochastic Differential Equations by Lawrence C. Evans
A quick, but very readable introduction to stochastic differential equations; that is, to differential equations subject to additive "white noise" and related random disturbances.
The Joy of Factoring by Samuel S. Wagstaff, Jr.
Readers of this book will learn the best methods of factoring integers, many reasons for factoring, and some history of this fascinating subject—and will likely have fun doing so!
Complex Multiplication and Lifting Problems by Ching-Li Chai, Brian Conrad, and Frans Oort
An ideal illustration of how modern techniques in arithmetic geometry can be fruitfully combined with class field theory to answer concrete questions about abelian varieties.