The other day I finished reading a really good book called ManHunt: the 12-Day Chase for Lincoln's Killer by James L. Swanson. I never knew (or didn't remember) that Booth wasn't acting alone: he was the ringleader of a larger conspiracy whose original plan was actually to kidnap Lincoln and take him into the Confederacy. Then when Lee surrendered at Appomatox, Booth and his co-conspirators changed their plans and created a scheme to kill not just the President, but also Vice President Johnson and Secretary of State Seward--all on the same night. In fact, General Grant was supposed to be attending the play that night in the same box as the Lincolns. If Grant hadn't changed his plans, he might have been there when Booth attacked.
It was a fascinating book. It appears to have been very well researched, and the author has a gift for narrative prose (this is coming from a reader who typically has trouble being interested in reading historical accounts).