Shigeru and Maruyama are awesome. So are Makoto and Arai. I think that's one of the trilogy's strengths/weaknesses: the protagonists are flat as pancakes, but the minor characters are great.

I'd totally buy the prequel and sequel, but have no room on my bookshelf. Put them on the floor! Or take two large books of equal height, put a plank of wood over them and presto! instant extra shelf! :D