The program is apparently used to prepare for various tests (SAT, TOEFL, GRE and such). I clicked on the TOEFL so-called "book", because I know somewhat of this test. To my surprise, there were only 300 words there ranging from "abandon" to "import" in alphabetical order. Where are the words after "import"?
In any case, I found a cool option to create your own book. In your own book, you can even add translations to a different language, in addition to the regular features. Now that feature is why I would use such a program. I used to make cards to learn new words. This would make it more fun, I think. Because it's not just cards; you can play games with those words.