Had a very good time with this manga. Enjoyed the art, the story, the characters, and just great stuff all around. It was very consistent too, most of the manga was strong. Even the "not-so-engaging parts" I'd say were necessary to set up the world so I get it. Now to talk ab the more specific stuff that I liked.
First off, Ken. Ken Kaneki is very interesting and I enjoyed getting to see his story develop. I still have a lot more to go but he was very compelling to read about. Watching him grapple with his inner ghoul side and the mental struggle that comes with it was very interesting and well achieved. Moments like the torture scene, Kaneki becoming the Centepe for the first time, and his meeting his inner child after fighting Arima were all amazing. If all of this was set up for the eventual payoff in Tokyo Ghoul: Re then I am all in.
Another thing I liked was the artwork. This is my first time reading a "horror" manga so some of the imagery stuck with me (in a good way). The illustrations were some of the manga's strongest points throughout the story and I can't wait to see Ishida's art style develop further. The side characters were also really good with names like Amon, Touka, Juzo, and Tsukiyama being my favorites. Love them all.
TL;DR It's a very good manga loved Ken and the artwork and can't wait for Re.