I took the pills in the car, and when they hit, they wiped out my memory of having taken them, so I took another two. I knew this because Amanda, my new then-girlfriend, said to me, “You already took some, Walt!” I believe the pills were Valium — I don’t remember now. My mother, a registered nurse, had recommended them to ease the misery of a kidney stone lodged in my left ureter, one of the pair of delicate, thin tubes that drain urine to the bladder. The pain when one is obstructed can range from a dull ache to how it might feel to give birth to a hacksaw. It was September of 2010, a cool, clear morning, the trees along the freeway already golden. We were driving from our home in Montana to Ketchum, Idaho, where I was set to speak the following day at a Hemingway festival at the public library. Ketchum is the idyllic mountain town where the stoic, troubled writer, fresh off a series of treatments for depression at the Mayo Clinic in Minnesota, blew his head off in the breezeway of …