The definitive reference on user-stories as a requirements and planning technique in Agile development, written by mike-cohn and published in 2004. This book systematized and popularized the user story format beyond the XP community where it originated with ward-cunningham's CRC cards and the early practice of writing stories on index cards.
User stories as a practice
mike-cohn's book defined the canonical form of the user story: "As a [role], I want [feature], so that [benefit]." The book explains acceptance-criteria as the conditions that must be satisfied for a story to be considered complete — connecting stories to the definition-of-done concept and to testability.
The book covers:
Relationship to XP
user-stories originated in extreme-programming as a replacement for traditional requirements documentation. ward-cunningham and kent-beck developed the practice of writing stories on index cards as a collaboration tool between customers and developers. mike-cohn's book extracted this practice from the full XP context and made it accessible to teams using any Agile method, including scrum.
This extraction was both valuable and problematic. Valuable because it spread a powerful technique. Problematic because, separated from XP's emphasis on acceptance-criteria and testability, user stories became in many organizations little more than wish lists written in the "As a user..." format without the verification teeth.
Significance
The book was the primary reason user stories became the de facto requirements format across the Agile ecosystem. It influenced scrum's adoption of the product backlog as a list of user stories (though the scrum-guide itself does not mandate the user story format). It also introduced many practitioners to relative estimation and story-points, connecting to mike-cohn's subsequent agile-estimating-and-planning.