I haven't read MANIAC (yet) but a few years back I was trying to find a good biography of Von Neumann and there are not many; the problem is that he's really difficult to cover comprehensively, even for science historians, because he impacted so many areas of science that you'd practically have to be a von Neumann to create a biography of von Neumann. One could probably get a rough idea of his intelligence by how many science historians it would take to create a comprehensive biography which explains his life and work to a reasonably intelligent layman.

It's less of a strict biography and more of a fictionalized story involving Von Neumann and his wife. As far as I can recall from my reading it was pretty historically accurate though.