HTML5 offers unique advantages to authors and publishers in comparison to both traditional word processing and desktop publishing tools like Microsoft Word and Adobe InDesign, as well as other markup vocabularies like DocBook and AsciiDoc. In this presentation, I explore three key advantages of an HTML5-based workflow: a lightweight production toolchain, optimization for digital-first content development, and WYSIWYG authoring for content creators. I also discuss HTMLBook, a new open, HTML5-based XML standard developed at O'Reilly Media, Inc., which is expressly designed for the authoring and production of both print and digital book content.