Upper beginners can get a lot out of this fascinating book, but it is probably best for those around the intermediate stage--those who have completed the basic level textbooks (Genki I & II or Minna Nihongo I & II).
As you can see from the scanned images, the book is much more than just a manga or even a good reader. It is a great reader and one that will no doubt leave you with a much greater understanding of Japanese grammar and vocabulary, but it really shines as a book on culture. It explores history, archaisms, dialects, and the heart of the Japanese spirit.
Enjoy Natsume Soseiki's Botchan in manga form with oodles of explanations and glosses.