Disclaimer: I watched the anime first, then picked up the manga where it left off. They aren't very different at all though. I fully recommend the anime as well.
This manga is an amazing feel good story about a bullied boy named Makunouchi Ippo who joins a boxing gym after being saved from a brutal beating by a strong boxer named Takamura Mamuro. The story then mostly follows Ippo and Takamura through increasingly difficult tests in their pro boxing careers.
The cast is not limited to only these two, in fact there are many other important rivals, and three other gym mates that all have expansive and very realistic motivations for what they do. In fact there are at least two fights in the story where I actually rooted AGAINST Ippo because his opponent was either way cooler, or had much more at stake.
If you like action, read Ippo
If you like realistic love storys, read Ippo
If you like amazingly fleshed out characters, Ippo is for you.
Even if you think boxing is a boring sport, i can wholeheartedly recommend you this manga, as it has a certain spark that you don't see too often these days