Steven Johnson, author of bestselling popular-science books including The Invention of Air, and a creator of TV and web media, is a local boy who graduated from St. Albans School. Like Walter Isaacson, Johnson is an expert on how the sciences and humanities intersect in numerous ways, and he can lucidly explain how the gradual accretion of many small ideas grows into the grand illumination of a true paradigm shift. Johnson’s broad appeal also rests on his grand maxim that everything correlates. He explains How We Got to Now (Riverhead, $30) by chronicling six keystone innovations that, together, paved the way for the modern world. Accompanied by drawings, photographs, and other illuminating and beautiful images, Johnson’s profiles of seminal technologies start with elements as basic as glass or light, and develop into complex systems—systems both technological and social. Working with “cold,” for example, scientists and entrepreneurs moved from 19th-century ice houses to refrigeration to air conditioning, ultimately making habitable many formerly unwelcoming environments.