I just finished the new book And On That Bombshell - Inside the Madness and Genius of Top Gear by Richard Porter. I liked the book very much and recommend it to anyone who enjoys the TV show. The book is filled with interesting and amusing stories about the show, told by the long time script editor.
Porter provides a satisfying meal of behind-the-scenes stories about Top Gear. The only other pieces I've read about the making of Top Gear was the 3-piece article written by Andy Wilman for Top Gear magazine after the show ended. I especially liked Porter's reflections on the gradual evolution of the show's format, writing, themes, and more. How they tried many things that resulted in big failures, many of which never made it to air.
Reading the stories about the early years of new Top Gear made me want to watch some of the older episodes from series 1 through 9, so I did. This site offers an easy way to watch those old shows.