It starts around 15 years before the first game. It deals with Andrew Ryan setting up Rapture, everybody moving in, Frank Fontaine coming in and his backstory, how they both started fighting over Rapture and it's eventual downfall up to a few months before the first game.
It shows Ryan formulating his plans or the city, meeting Bill McDonagh who is one of his few friends and it mostly shows the view points of Bill, Ryan, Fontaine and a few others as it progresses. We get to see how the ADAM and EVE was found and used, see how Suchong and Tenebaum worked and how the splicer war started and eventually went bat**** crazy.
It also deals with the creation and "education" of you know who, along with how the Big Daddies and Little Sisters were made. All in all, a great read and well done.
I also found the Bioshock Infinite book too. So I'll be giving that a read as well.