Elementary geometry is a rich and highly interesting subject of mathematics that contains typical knowledge elements such as statements of theorems, geometric relations and their algebraic expressions, and diagrams of configurations. Effective processing of these elements requires logical reasoning, symbolic and algebraic computation, and visualization tools. The diversity of knowledge elements and the need of sophisticated techniques to deal with such elements make elementary geometry a unique and ideal subject of study for mechanization and automation. Indeed, automated geometric reasoning and dynamic geometry software have witnessed remarkable developments in the last three decades. Traditional textbooks are standard documents that present domain knowledge elements in a structured, systematic, and logically sound way. They have played an indispensable role in education and research. To make the contents of textbooks dynamic, manageable, and processable by available software tools, we have developed a new type of textbook, called GeoText, which is a running software system rather than a static document. With GeoText, textbooks can be created, modified, updated, presented, and printed at any time. Based on the use of formalized geometric knowledge data and the integration of powerful methods and software tools of algebraic computation, automated deduction, and graphical presentation for computer geometry, GeoText has achieved a high degree of automation in functionality and intelligence in behavior. The current version of GeoText is restricted to plane Euclidean geometry. The textbook authoring and content management system has been implemented, mainly by the first author, in Java according to the theoretical framework and design principles described in [1]. The system is supported by a structured and formalized knowledge base GeoData [4], created initially by L. Qiao and being expanded and refined by the authors and their coworkers. It has integrated GEOTHER [7], a geometry theorem prover developed by the second author, and GeoDraw [5], a dynamic diagram generator developed by the third author, with an interface to the dynamic geometry software GeoGebra [6]. GeoText is capable of assisting the user to create and organize geometric knowledge data as textbook contents, presenting structured textbook contents as electronic textbooks (in English or Chinese), checking the consistency of the presentation structure and the redundancy and completeness of textbook contents, discovering relations among geometric knowledge data, proving geometric theorems, and generating dynamic diagrams for configurations in textbooks. Most of the tasks can be carried out automatically or semi-automatically. The functionalities of GeoText on content management and knowledge processing will be discussed in detail in the following two sections.