The days of the printed textbook are numbered. Recent advances in technology (Flash, Web2.0 applications), learning theory and approaches (Constructivism, Multiple Intelligences, Differentiated Instruction, Universal Design for Learning), cognitive sciences (Distributed Cognition, brain research), and other forces have come together to form a paradigm shift in the way teaching and learning can occur in the twenty-first century. There are currently several different variations or definitions of "digital textbooks." Unlike the passive, printed textbok which can only be read, the interactive digital textbook features animation, audio, video, graphics, and is hyperlinked to other resources. The accessbility and adaptability of digital textbooks are another reason for their superiority over printed text. Though scarce research supports the effectiveness of digital over print textbooks, publishers, nonetheless, are producing moreand teachers are demanding more of them. Future trends in digitial textbooks include customized publishing, wikis, and Augmented Reality.