What's great is that each medium has a unique set of things that it does and does well. Film is a visual medium, and obviously, you can't fit a whole book into two hours unless you're really economical about it. Obviously, they say a picture is worth a thousand words, and on some level, it's sort of true.
I'm very good at compartmentalising my life. I did motor-racing for a while, stopped, didn't miss it. I did power-boat racing for a while, stopped, didn't miss it. I had such a good run at the BBC. I had a hell of a CV with arguably the greatest broadcasting organisation in the world. But I've never missed it since.