The notion of the book is becoming increasingly elastic as publishers mash up text, video and Web features, or enable conversations among readers.

Simon & Schuster is releasing four “vooks,” which intersperse videos throughout electronic text that can be read and viewed online or on an iPhone or iPod Touch. In “The Amanda Project,” HarperCollins has invited readers to discuss clues and characters on a Web site,and as the series continues, some of the reader comments may be incorporated into minor characters or subplots.