I'm still about to finish Genki II (those couple of chapters about honorific and humble speaking are killing my will to study lol) and after that I'll pick "An Integrated Approach to Intermediate Japanese" because sincerely I liked how the Genki series are structured, the explanations etc.. and after a quick look at "An Integrated Approach to Intermediate Japanese" I decided I will go with that. Because I like so much those books I was thinking I could buy also the 4th book in the serie, Authentic Japanese: Progressing from Intermediate to Advanced. So anyone know this book? Amazon has a preview but I'm too low in level to judge if it's a good book. Also, there is this book, anyone know it? How it is in level?

PS: I'm not neglecting real japanese, but still I like textbooks so... what do you think about those I mentioned before?

I have a copy of Authentic Japanese: Progressing from Intermediate to Advanced, as well as Rapid Reading. It has been maybe a year since I looked at them, but I remember at the time not finding the content too interesting. During this phase (passing N3 and studying for N2)I preferred the main Tobira book and the Tobira grammar book, along with regularly reading nhk, lifehaker.jp, etc. I've never used Genki, so I'm not sure what level you're at after the 2nd book, but I would assume Tobira would be a good fit.