Quick thoughts on Diamond is Unbreakable:

After the epic journey of Jotaro Kujo and his friends in Stardust Crusaders, Jojo Part 4 transports us to the much more "tedious" Morioh, a small town where Josuke Higashikata, the user of the stand Crazy Diamond, and many other stand users live. Due to the fact that stand users attract each other, the city suddenly becomes flooded of people with the most assorted types of abilities; one of them being a killer, that's been terrorizing the city for a long time.
That way, Diamond is Unbreakable sets its mystery tone right from the start; but even though the pacing of the story is nice, it takes some time to really show what it came for at the beginning. However, each chapter is more bizarre than the last, adding unique characters and the most peculiar circumstances, while still keeping the battles of wits from the other arcs; ghosts, aliens, cat-plants... anything can show up, but still feels well-placed.
I believe the best aspect of this arc is how it handles the characters: We're introduced to a lot of them, each one with it's distinctive opinions, relations, motivations and stands; but instead of focusing specifically on the "main party", this arc manages to offer a significant amount of screen-time to their development, without deviating too much from its subject.
In the end it manages to combine comedy, action and mystery perfectly while delivering nice interaction between everyone, creative situations and immersing us in a very relatable universe with very relatable characters. Some slow chapters weren't enough to lower my enjoyment and were quickly forgotten after the breathtaking climax it had. Diamond is Unbreakable was an awesome experience and I would love to see it animated as soon as possible.