These are the textbooks that I used to start learning Japanese myself. I would definitely recommend them. Keep in mind that this is
elementary Japanese, so GENKI will only lay down the foundations for you to build the rest of Japanese on top of it. When you finish GENKI II, you should be at a JLPT 3 level, which is far from fluency. The Japan Times has also put out some
intermediate level books that look very helpful. They are a bit pricey, so I have not managed to get my hands on them quite yet.