This is a really great book about the potential of hydrogen for both energy production and as a transportation fuel. Romm does a great job explaining the roadblocks hydrogen faces before it becomes a viable fuel for cars. Joseph Romm was acting assistant secretary of energy for energy efficiency and renewable energy during the Clinton Administration, so he's a very well-informed source of information on the subject. It's a great book - one of my favorites. If you want to learn about hydrogen technology, this book is a great start.