River of Shadows is part biography of Eadweard Muybridge, an English photographer known primarily for his use of multiple cameras to capture motion, and the development of the zoopraxiscope, an early device for projecting motion pictures. But it is also a larger story about the acceleration and industrialization of everyday life in the nineteenth century, such as the birth of the railroad. Solnit uses Muybridge as way of looking at the connections between art, technology, and politics.
There's a hard to find film about Muybridge that I had the privilege of seeing a couple years ago that animates his motion studies (not, apparently, the way audiences would have seen his films via zoopraxiscope, as those had to be drawn). This book goes into a little more detail about his background, but there is little known about him. It seems he was a solitary and private man who devoted his life to his art.