Two, it's irrelevant to the points argued in this book.
Ricks doesn't look too much at why we invaded. He's addressing HOW we managed Iraq after the invasion. It should be a matter of obvious record that that has been a "fiasco." What happened in Lybia has nothing to do with this.
At the time that you seem to believe there was a "strong justificaton" for invading Iraq there were multiple intelligence experts trying to stop Bush from misrepresenting the facts. (I'm being generous in my characterization of Bush.) One such person was Vincent Cannistraro, former head of CIA Counter Intelligence and former head of the NSA. He's no small fry in the intelligence community. Months before invasion he stated how the Bush White House was using "cooked information" to justify an invasion and how it was essentially ordering the CIA to only offer intel that supported an invasion.
Even Colin Powell has now come forth and admitted that his worst hour was his presentation at the UN.
The only justification was in the neocons' mins. It had nothing to do with reality.
As for Gaddafi, I still stand on "proof." This isn't a mathematical equation we're talking about here. There's almost never one path to a solution. And there's frequently never a single cause of anything.
And besides, Gaddafi hasn't exactly been a major threat. Before the Iraq invasion we knew that Iran and NK were major threats - and Bush's actions have most assuredly made us weaker in facing those threats by getting our military bogged down in a quagmire and by sheer incompetence in all things diplomatic.