I dug this book out of my library after finishing Walter Isaacson's book on Einstein. Infeld explains special and general relativity with the clarity that only a physicist can summon. The book, though over sixty years old, sheds light on Einstein's work using basic concepts that anyone with a rough memory of high school physics can understand.
Some of the information in this book may be outdated but as someone with only a casual interest in physics, I can't really speak to that.