This is, for my money, the most successful volume of the series thus far. The same problems remain, but for the first time we see the core, emotional differences between Shizuku and Issei, which gives us a better idea of what the true stakes are for them: Shizuku has known a warm family (notably with his mother, not his jerk dad), while Issei has not. The difference, therefore, is that Shizuku is trying to understand the father he never connected with and whom he felt never saw him for himself; Issei is trying to find a father he never had.
It certainly helps that Issei has been getting more likable since Loulan entered the picture. I'm still not sold on the series, but when it doesn't solely rely on the wine aspect, I can see more of its appeal.