Taskbook is described as 'By utilizing a simple and minimal usage syntax, that requires a flat learning curve, Taskbook enables you to effectively manage your tasks and notes across multiple boards from within your terminal' and is an app in the Office & Productivity category. There are five alternatives to Taskbook for Linux, Mac, Windows and Vim. The best alternative is Taskwarrior, which is both free and Open Source. Other great apps like Taskbook are TaskLite (Free, Open Source), dstask (Free, Open Source), vim-taskwarrior (Free, Open Source) and ETM: Event and task manager (Free, Open Source).
TaskLite is built from the ground up to be a command line task manager. It's functionality is similar to Taskwarrior but with a simpler codebase, reduced complexity, faster performance, and more active development.