A computer network based digital information library system employing authentication and encryption protocols for the secure transfer of digital information library programs to a client computer system and a mobile digital information playback device removably connectable to the client computer system. The present invention is a computer network based library and information delivery system for accessing and obtaining selected digital information files. The library and information delivery system comprises: 1) a library server having a plurality of digital information files; 2) a client computer system coupled to the library server over a network; and 3) a mobile device removably connectable to the client computer system, the client computer system including logic for requesting a download of a selected one or more of the digital information files from the library server, the client computer system further including logic for downloading the selected one or more of the digital information files to the mobile device.