Ive been studying Japanese for six years now and never have I learned more about the language than from reading this!
It forces you to learn kana, giving you a huge leg-up in your reading skills, it teaches you about not only grammar, but how the Japanese think, and thus why the language is how it is, and it does it simply, plainly, and succinctly!
There really is nothing better!
Schwerigkeit about Learning Japanese, v2.0.2