So recently I purchased a kindle touch, and I thought one of the great things I could use it for would be to carry around a japanese text book. I have previously used minna no nihongo and Japanese for busy people, and frequently needed to re-lookup a grammar point or conjugation. I already have JED for my android phone but it is really only useful as a dictionary, what I want is an actual textbook with lessons and explanations in it - preferably aimed at an upper beginner to intermediate level.
However despite my searching online for hours I have not been able to find any ebook versions of the more popular/recommeded Japanese text books, and the textbooks i did find were aimed only at absolute beginners.
So I'm wondering does anyone know of a good Japanese textbook that comes in electronic format which they can recommend?