Again!! has been an amazing and rereshing read, right from the beginning. I strongly recommend giving it a try, particularly if you're looking for something creative, a bit wacky and mixed with very strong character creation and a versatile, ever changing plot with time travel questions thrown in.
Particularly in recent chapters, Kubo-sensei has gone with a twisted plot approach that really embodies her style and has a very nice effect, in my opinion. Even in earlier volumes, it was hard to predict where she was going, some, like volume 3 getting a bit boring and others like volume 4 seeming to hit so many different ideas and not close all of them off. This style, however, makes for a fairly realistic storyline, if a sometimes difficult one to follow.
In other words, Again!! isn’t a standard plot progression and even the characters don’t follow a steady development pattern. The characters aren’t even constant: for much of volume 1 and 2, Aki was as important a character as Imamura, in volume 4, Hiro was suddenly introduced and became important, then disappeared, in volume 7 the character relations all get jumbled up and, if you look at the cover of volume 8, you will see that another, brand-new character suddenly becomes an important face.
If you look at Kubo’s other series though, they have a similar feeling – Kubo doesn’t like conclusions, she writes her stories to start new issues, introduce more characters and ideas and sometimes she closes them off, sometimes she just moves on. You could argue it’s terrible story telling technique, or, if you get too invested in a particular aspect of the story, you might think it's filler or milking the plot but it's probably just Kubo-sensei's quirk and enthusiasm to throw her characters off in different directions, which, if you can appreciate it, always keeps her series fresh and pretty realistic (since I find that real life rarely has neat conclusions either)
So the one word of warning would be that you can't go into this series expecting a neat conclusion after a linear plot progression. You're in this for new things and often dropping old arcs without any warning!