In each chapter, a new grammar and new vocabulary is presented that to be learned and you need not to lose in the remaining chapters to connect. Towards the end of the first book, it is asking a little more difficult and with Book II by the learner bite, as some chapters bring many new details, but essential for learning the language are.
If you learn very thoroughly, and this should be, I quote for each book 1-2 months, depending on the pace of learning. So you can for about half a year already properly say what and a great foundation for further language learning has settled.
Book IV is ordered, I'm very excited.
Note: The book is completely in English. General English skills should be present.
Thank you for your attention your /. :)
Have a nice day to you and have fun while learning the language. :) :) :)
Best Regards,
Sebastian