The author (Jimmy Lerner) committed murder, or manslaughter—depending on your conclusion based on the evidence presented at his trial.
The crime occurred after Lerner and his friend/lover, Slavin, went to Vegas for a getaway, checking in to the Sundowner hotel in 1998. In the hotel room, Lerner attacked Slavin, claiming the latter had threatened his family, and killed him with a belt and plastic bag. The author has made statements indicating he was acting in self-defense and was high on drugs, and he pled to voluntary manslaughter.
He was sentenced based on evidence that he did commit a crime, and the victim's sister later sued Lerner. The case reached the Nevada State Supreme Court, where it was dismissed. She was attempting to recoup any profits Lerner had made from the publication of his first book (You Got Nothing Coming).
Lerner claimed in his book that his victim was well over six feet tall and two hundred pounds; in reality, Slavin was 5'4" and slightly built. Other inconsistencies cast doubt on the crime being self-defense or manslaughter. For example, the police report noted that Lerner had no injuries except swollen hands.
Given the likelihood that Lerner has sociopathic tendencies, and the fact that he only served two and a half years of a twelve year sentence (he was paroled in 2002), it's unlikely he learned much. He states that drugs played a big part in his crime, so perhaps he learned to stay sober. It's also possible that reflecting on his crimes, as he did in the book, may have helped him turn his life around.
It would be interesting to know what Lerner has done with the money he earned from publication of You Got Nothing Coming.