QUARTET I is an intermediate Japanese textbook covering Lessons 1 to 6, roughly equivalent to JLPT N3. It's published by Japan Times, the same team behind GENKI, and designed as the next step after finishing a beginner series. Each lesson is built around a single theme and works through all four skills: reading, writing, speaking, and listening. The reading section introduces the grammar and expressions, and the other sections build on the same material, so everything connects.
The book is almost entirely in Japanese, with English used only for grammar explanations and vocabulary translations. This is a significant jump from GENKI. Grammar at this level is less about core rules and more about nuance and usage. There are also elementary grammar reviews and kanji strategy sections built in. Audio is a free MP3 download (150 minutes) and also available through the OTO Navi app. There's a separate companion app for vocabulary and kanji practice.
It assumes around 250 to 300 hours of prior study, which is roughly where you'd be after completing GENKI I and II. Reviewers consistently note it's a smoother transition from GENKI than Tobira. The speaking and writing sections assume a classroom. Self-studiers will need to find other ways to practise output, but the reading and grammar sections work well alone. The workbook, the Quartet Vocab & Kanji app (iOS/Android), and the detachable vocabulary supplement (good for feeding into Anki) help fill the gap. But at this level, spending time with native material outside the textbook starts to matter as much as the textbook itself.
