"I Want to Tell You,"O.J. Simpson's instant book, hit stores across the country today, along with a tape version. Presented as his response to the 300,000 people who have written to him in jail, the book was co-authored with Lawrence Schiller, a freelance writer who also collaborated with Norman Mailer on the Pulitzer Prize-winning "The Executioner's Song." O.J. writes: "I could never kill anyone, especially Nicole," and complains of an untrustworthy legal system and a sensationalist and racist media. He says he would "jump in front of a bullet" to protect his ex-wife. Much of the book alternates between letters received in jail and Simpson's responses. He portrays himself as a spiritual man and a victim in the whole affair, and accuses the press of being unfair to him. A TV trial, he says, poses special problems: "Having these TV cameras in the court all the time is a no-win situation for me. If I'm looking like I'm having a good day in court, if I'm too jovial, people say he's not serious or concerned enough. If I'm looking worried or upset, then it looks like I did it. For those who read all the way to the end, the back contains a chronology of his life -- beginning in 1949 ("O.J. gets rickets") to 1989 ("Nicole calls 911 on New Year's Eve"). Simpson's book was published by Little, Brown & Co, a subsidiary of Time Warner.