Before I delve into which books I recommend I should define who these books are intended to. Intermediate japanese textbooks in general tend to market to people who have finished the genki or minna no nihongo series, in other words you should be past JLPT N4. If you’ve used other Resources to study and you’re not quite sure at what level you are at, you should take some sample N4 questions online to determine roughly where you are at. If you’re passing with flying colors(70%+) you can probably jump into the textbooks I’m recommending in this article.

An Integrated  Approach to Intermediate Japanese

First one on the list is one of the most popular choices, it’s actually the same company who did the genki books so the transition from the genki series to AIAIJ is very smooth. However, there is some criticism to this book. One common complaint is that the conversations in the book are dull. It’s however a good book if you can look past the dull conversations as the book does as it promises. You should be at JLPT N3 level after finishing. The teaching style is very similair to the original genki books. I recommend picking up AIAIJ over the other intermediate books if you used the genki books(and like the format, obviously if you didn’t like the genki books you should really consider picking another book)

Minna no nihongo Chukyuu

Rarely gets mentioned even though minna no nihongo shukyuu are common most people don’t pickup the chukyuu books. I don’t exactly understand why, I personally studied with this book and I actually preferred it to AIAIJ(however, both are good and I’m only preferring minna no nihongo by a small margin).

Tobira: Gateway to advanced japanese

I personally never used this book but I skimmed through it and my impression is that this might be the best of the bunch. However, the transition from genki series or minna no nihongo to Tobira can be difficult. Also Tobira puts you even past JLPT N3 when you’re done with it. Not all the way to JLPT N2¬† but not far from it. You will know over 800 kanji when you’re finished. It’s one of the harder intermediate books but also packs more vocab and grammar.