Orbifolds and Stringy Topology - Adem, Alejandro (University of British Columbia, Vancouver) a Leida, Johann (University of Wisconsin, Madison) a Ruan, Yongbin (University of Michigan, Ann Arbor)

An introduction to the theory of orbifolds from a modern perspective, combining techniques from geometry, algebraic topology and algebraic geometry. The heart of the book is a detailed description of the Chen-Ruan cohomology, which introduces a product for orbifolds and has had significant impact.