Elliptic cohomology is an extremely beautiful theory with both geometric
and arithmetic aspects. The former is explained by the fact that the
theory is a quotient of oriented cobordism localised away from 2, the
latter by the fact that the coefficients coincide with a ring of modular
forms. The aim of the book is to construct this cohomology theory, and
evaluate it on classifying spaces BG of finite groups G. This class of
spaces is important, since (using ideas borrowed from `Monstrous
Moonshine') it is possible to give a bundle-theoretic definition of
EU-(BG). Concluding chapters also discuss variants, generalisations and
potential applications.