This course is much better than any book, why? It's interactive. There's no need to lookup terms you don't understand just mouseover to popup the glossary term wherever you see the double underline like thisThrough The Lens. A term applied to viewfinders and metering systems that operate behind the lens. As such TTL is accurate because it sees what the lens sees. . You can filter it for the level you are at. And of course it's more eco friendly than any paper book!