For one of Superman's greatest villains, this compilation does little to deliver on the hype. The problem is that these stories, written from 1958-2000) are not done with anything remotely close to continuity. Brainiac is an alien collector of cities, then a silly plot-motor, then an evolved robot, then remade into a Cthulhian intelligence, then (after the 1986 Crisis) a disembodied spirit of a smart alien scientist possessing a mentalist, then... I don't know.
But there's a lot of backstory that's missing, and I am sure Brainiac's ever-revolving origin story is not yet done, as long as there are comics to be sold. The only high point here was to see the introduction of the City of Kandor, and Supes' first interactions with this green baldie.