I've read a lot of Mitsuru Adachi's works and Katsu! is among my favorites. Like most of his newer works, Adachi sets out to establish the main relationship from the start, and builds up this relationship throughout the series - it's even touching to know that both characters had feelings for each other before they became friends. Lots of Adachi's trademark humor, self-insertions, and a good tie-in to the sport gimmick (in this case, boxing). In addition, the antagonists/rivals are actually pretty decent guys, you don't root for them, but you don't hate them either - you want them to be successful in their livesas long as they don't steal the girl away from the boy.

Unfortunately, which is typical with Adachi, the ending is abrupt and leaves a lot of things hanging (particularly with side characters). But that doesn't spoil the overall work.