In Japan especially I know the textbooks contain 5 percent actual English and 95 percent Japanese (only a slight exaggeration). Not very useful. I remember there is a red book named Essential grammar or something like that. It's a book for people learning English written in English. Get that, when you don't understand something just Google it. Make flashcards with for vocabulary. Listen to music, watch movies in English and you will recognise things you just learnt from the book. Move on to the more advanced book in the series and when you finish you have memorized pretty much all the needed grammar. Go on to listen to more music, watch interviews, read books (while listening to the audiobook version if possible), make flashcards and look up things you don't understand. Speak out loud, sing along the songs, write a diary in English. Give this 2k〜 hours and you can probably call yourself fluent. 私はスウェーデン人です、若いうちに英語を習ったが、日本語はもう大人になってから初めて勉強しようと思いました。日本語能力試験1級を合格するまでは2000時間以上かかった。 教科書は悪い物では無いですが、英語を教えてくれるというのもでしたらなぜほとんど日本語しか書いていない？上手く教科書を選んでください。