Fulton on Algebraic Stacks

William Fulton is writing a new book on algebraic stacks. He is posting each chapter online as he finishes them. So far he has posted the preface and the first chapter.

For an introduction to the concept, see Dan Edidin’s What is… a stack? from the Notices of the AMS, and for a more detailed introduction, try Introduction to algebraic stacks by Alberto Canonaco.