First, it is good. I can't say if its influential, but it has been ongoing since 1987 (Though in 2004 they "Ended" it with the 6th part, only to retcon a spin off reboot as cannon, so its still going!)Laughing Banana said:
With it being over 700 chapters, its a bit hard to give a summery of it. The closest way I can think of describing it is the adventure of the Joestar Family line fighting various enemies with super natural abilities.
The series can be broken into 7 parts right now, with clear starts and ends, each with a different main character and cast, though with Part 3 taking place in the 1980's, parts 4, 5, and 6 have more recurring characters in them.
Part 1 wasn't that great, but Part 2 is fantastic and the rest of the series goes up and down between "pretty good" and "awesome", with the fact that the series has multiple parts allowing the author to keep the series fresh (Though parts 3 and 5 feel dragged on, while 4 feels like it was cut 2 years short)
It is also a bit notable for being the longest running manga in Jump to never get a normal Anime, although it has had an OVA of the 3rd part and a movie of the first part.
Here, maybe this image will give you an idea about the scale, This is from the first page of part 6. Er, don't read the text to much, spoilers and all that. Try and stay clear of the stuff on the left, look at the floating heads, and years on the right.:
(Also, I think Jorge is a mistranslation to try and add a Jo to there names, since earlier flow charts and all of part 1 called him George)
