Actually, a detective who had been investigating the OJ case for 30 or so years came to the conclusion that the probable killer was OJ's oldest son Jason - his son from his first marriage. I think the tile of the book was something like "OJ was innocent and I can prove it".
Allegedly, Jason had been treated for mental illness involving violence at least twice. At the time of the murders he was on probation for attacking his former boss with a knife, out of the set of chef's knives he always carried with him. He was also a friend of Nichole and spent a fair amount of time in her company - On the evening of the murders, she was supposed to be a guest at the restaurant where he was a chef.
The book documented all of his theories in detail (about 600 pages worth) and appeared pretty convincing.
The interesting part is that no one tried to rebut the contents of the book. The people you would expect to care simply ignored the book completely.
It's kind of like the original trial where the defense claimed that the LAPD was bigoted and framed people for crimes they were not guilty of. Then we had the Rampart scandal where a member of the LAPD testified that they were bigoted and framed people and planted evidence to convict the not guilty.
And most of America decided screw the evidence, he's guilty.