The Epigraph Trilogy is basically the manga version of Steins;Gate 0.
I quite enjoy the story so far despite it still being a bit of a mystery and what the protagonist's objective is is unknown. However, this is only the first part of the trilogy and knowing Steins;Gate, they'll probably connect everything together later on.
I personally don't think the artstyle is that great and it's much more different than the artstyle in the anime and visual novel. But it's not neccesarily bad, just not my taste. However, I didn't think too much of it since the art didn't really affect my enjoyment negatively.
you loved the characters in the original Steins;Gate as I did then you will love them here as well. it's quite a refreshing sight to see all of them in different clothing and new characters are introduced. The way the creators changed Okabe Rintaro's appearance and personality was really good as it fits with his depression. This was pretty shocking to me because I was so used to the chuuninbyou Hououin Kyouma. It felt weird but it made the story more interesting.
This is what you would expect from the Steins;Gate franchise and I can't wait to read the rest. Hopefully I'll have a mindblowing experience just like I had in the original!