I never watched much of the anime series. But I can tell it's a good one by reading the manga. The original Trigun manga has only two volumes which is a bummer, but it continues in a series called Trigun Maximum. This manga series tells some of the journeys Vash has had in the anime.
The stories in volume one have some great moments most of which are humorous. However in the volume two, Vash is more seroius and there aren't many funny moments in it. So that basically takes away some points. But the characters are still great at least.
If you like the anime series, you might like the manga version. Or maybe the Maximum version of the manga. Whatever you choose is up to you. Read it and see for yourself.