>>501677>>501682There's a better explanation:
Carine, who was a valuable source for both Krakauer's book and Sean Penn's movie adaptation, had shared this dark family history with Krakauer back in the early 1990s, though strictly off the record in order to protect her parents "from full exposure in case they could change for the better." (Not surprisingly, they didn't.) And even though it compromised his book, Krakauer honored Carine's restrictions. Instead, he hinted at the truth with repeated allusions to an "overbearing" father, which some readers caught, though many did not.
The Wild Truth opens with several harrowing scenes. After vividly describing one of their father's attacks on her mother, McCandless moves on to the double beatings she and her brother suffered, "forced down, side by side" across his lap. She writes, "The snap of the leather was sharp and quick between our wails. I will never forget craning my neck in search of leniency, only to see the look of sadistic pleasure that lit up my father's eyes and his terrifying smile — like an addict in the climax of his high."
Fortunately, McCandless — while searingly honest — doesn't sustain this level of distressing intensity, or I doubt I would have been able to make it through. What she does do is chronicle Billie and Walt McCandless' miserable wine- and gin-fueled marriage and its lasting repercussions on their children.
http://www.npr.org/2014/11/11/363120048/behind-the-famous-story-a-difficult-truth 
