Not sure why I haven't heard of JJBA until very recently, but I watched the new anime for the first season and decided to try out the manga so I started with part 3 and, let me tell you, it was one hell of a ride.
You should know this already (if you don't then here it is), but here's a quick brush up on what JJBA is. It's a manga that has been around for an extremely long time and is very popular. It contains lots of action, gore/blood shed, super bulked up men, and each protag has the nickname "Jojo" hence why it's called Jojo's Bizarre Adventure.
This particular part of the long running series was truly an adventure. The story spans about 50 days and the group of heroes on this journey must reach the ultimate antagonist at the end or else the protag's, Jotaro Kujo, mother will die. While most of the story seems to be filled with meaningless encounters, these are still very much entertaining. It's not a super fast paced story, but it runs well enough and is clear in its intentions through and through. I give story an 8.
Now, many people are put off by the art style in JJBA. Personally, I was drawn in by its art style because I assumed this series was going to be funny and that the bara men were going to add to the comedy. I found the art style fairly consistent and I still liked it even if it didn't fit normal standards. I give art an 8.
On to characters. One of my issues with JJBA is the lack of strong female characters. From Part 1 to 3 most of the female characters were either the potential love interests or the family members who generally didn't play a huge part in the adventure. However, despite this I found most of the characters to be interesting and enjoyable since they're filled to the brim with their own quirks and are all pretty easy to grow fond of. For example, at first I felt neutral about all the characters that I didn't know yet. There was nothing about their appearances that made me like them immediately, but as I read on I began to appreciate all of them a lot more which made major losses really hard for me. Even if you don't feel the same way I do you'll at least enjoy their reactions and interactions throughout the story since dialogue can be extremely funny. I give characters a 9.
Enjoyment? Did I enjoy JJBA part 3? Hell yes. It was jam packed full of comedy, great characters, an interesting story, and good art. I have be recommending the entire series to many of my friends since I started reading Part 3. I think Stardust Crusaders really sold this entire series to me. I enjoyed it. 10/10.
Overall I give it a 9. It's not the BEST manga out there, but it sure as hell is one of the better ones.