A book that helps a lot to learn the basic kanji as an N5 and N4 student. Written very nicely with self-contained lessons so you can do it whenever you can and want (although you always need to go back a bit for review). It is followed by Kanji from Zero 2 with many more advanced kanji.

Overall, the From Zero series (see Japanese From Zero) has helped me a lot. Knowledge of English is a prerequisite, of course, to read it. I also go to a language school, so I can't guarantee that you will learn Japanese from this series, but it is definitely a good start, a helpful aid, and it helps you realize if you really want to spend more time learning Japanese in the future. I recommend it.