Bush "has a way of falling back on the hazy memory to protect himself from potential political embarrassment. In other words, being evasive is not the same as lying in Bush's mind … It would not be the last time Bush mishandled potential controversy. But the cases to come would involve the public trust, and the failure to deal with them early, directly and head-on would lead to far greater suspicion and far more destructive partisan warfare."
McClellan writes that he was sincerely defending President Bush through his three years as the White House press secretary but that he was misled following the CIA leak case involving Valerie Plame.
The "jumping-off point" for the book, he writes, was in 2003, when the CIA officer's name was revealed to reporters.
McClellan says he was duped into officially denying that any members of the administration were involved in the leak.
He says he unwittingly took part in defending Rove and Lewis "Scooter" Libby, the vice president's former chief of staff.
"I spoke with those individuals, as I pointed out," McClellan said to the press on Oct. 10, 2003. "And those individuals assured me they were not involved in this — and that's where it stands."
McClellan characterizes the White House denials as a "deception," claiming he was told Rove and Libby were innocent.
McClellan said that when his words were exposed as false, "I was constrained by my duties and loyalty to the president and unable to comment."
Now, he said that he was "at best misled" by Rove and Libby.
McClellan also condemned the administration's delayed response to Hurricane Katrina, saying the White House "spent most of the first week in a state of denial" and "allowed our institutional response to go on autopilot."
Some of his harshest criticism is reserved for Secretary of State Condoleezza Rice for being "sometimes too accommodating" in her first term roll as national security adviser. He writes that she made an effort not to offend anyone and carefully worked to protect her own reputation.
"No matter what went wrong, she was somehow able to keep her hands clean," McClellan writes. "She knew how to adapt to potential trouble, dismiss brooding problems, and come out looking like a star."
ABC News' Jake Tapper contributed to this report.