Structural Readers are graded in six Stages according to the following principles:
The structures of the language are introduced in the same order as in the majority of modern course books.
2. The vocabulary is controlled as in other series, with the important development that words required for special purposes are included freely by a prescribed process of repetition.
What is interesting is that the simplistic plot includes a lot of themes from other science fiction, such as "2001 A Space Odyssey", "The Matrix" and "I, Robot". This includes smart computers who rebel on their master humans and try to dominate the world.