Little Book of User Stories: Heuristics for requirements in an agile world
This book was written because, while User Stories look easy, I found I was answering the same questions again and again.
Questions like: “How do I make my user stories smaller?” / “What is the right size for a user story?” / “What is the difference between an Epic and a Story? And where do Tasks and Sub-tasks fit in?” / “Who writes user stories?”
Listen the Little Book of User Stories FAQ for free (18Mb, mp3, 12 minutes.)
The first three chapters of Little Book of User Stories for free as a PDF via LeanPub.