Modular Forms
Cohen, Henri / Stromberg, Fredrik
This comprehensive textbook, which includes numerous exercises, gives a complete picture of the classical aspects of the subject, with an emphasis on explicit formulas. The heart of the book is the classical theory developed by Hecke and continued up to the Atkin-Lehner-Li theory of newforms and including the theory of Eisenstein series, Rankin-Selberg theory, and a more general theory of theta series.