I use it. the format basicly consists of a list of modules (lessons or reviews) to work though. each lesson module starts with a short test on how to solve the

I use it. the format basicly consists of a list of modules (lessons or reviews) to work though. each lesson module starts with a short test on how to solve the problem it teaches, 1-2 worked problems and 2-3 problesm then more short text on how to solve some variation of the problem coupled with 2 solved problems and 2-3 for you to solve. review modules just give you a few problems to solve. if you can solve 3 without making any mistakes, it will finish the module and you can go tot he next one. every few days you are presented with a quiz that tests what you know and genearates review modules for you to go though before retesting you. overall, it seems spartan but its effective. you spend most of your time actuvly engaing with the problems with just enough information to solve them. the structure of the courses are setup such that you learn and master prerequisites before you are presented a lesson so there isn't much of the frustration you might find where a problem implicitly assumes you know something you don't. That a big reason they start you with a placement test. overall I'd say the $50 price tag is worth it. its very efficient vs reading and working though problem sets where you don't necessarily know what you need to know to solve them. you're not spending time figuring out what your knowledge gaps are as it fulls them in as you go for you.