There's the Trigun manga, which is relatively faithfully adapted by the original anime. I think it had six volumes. Not 100% sure on that because I bought the omnibus versions which I believe were three volumes each. That leads into Trigun Maximum. The first few volumes of that might be adapted by the anime, I forget exactly where the deviation occurs, but there is a massive deviation as the anime goes on like tended to happen fairly often back then.
I'm not the biggest fan of Maximum. Trigun was pretty well done and easy to read but I just couldn't keep up with what was going on when it came to Maximum. I'm not sure if that comes down to the translation, the art, or a mix of the two. A couple of years ago I saw one of the translators talking about how they had a lot of trouble with it as well. I never did end up finishing it.
I'm not sure if there was a re-release or anything. At the end of the Trigun omnibus volumes it said that eventually there would be Trigun Maximum omnibus releases so you wouldn't need to buy them again if you were buying the individual volumes as they released. I never did see Maximum omnibus volumes so I'm not sure if those ever actually happened