Two years ago, while walking, I fell — bam! — on my right knee, shattering my femur against the artificial knee I’d had installed five years earlier. First I felt amazement, then pain, then the existential dread of lying on the street wondering if anyone would hear my cries for help, then the ambulance, then my surgeon, then a brand new artificial knee, a larger one with an eight-inch rod that fit inside my femur. I was alive, grateful and bullish about rehab, but my ramblin’, dancin’ days were over. I’d walk again slowly but not far. Still, walking, as so many people have discovered during the coronavirus pandemic, is freedom. Three new books remind us that it’s also so much more.