In the 200th anniversary year of his birth, and 150 years after his book on the origin of species, Charles Darwin remains the most controversial and in many ways influential scientist of the 21st century, as he was of the 20th and 19th.

Darwin and his theories are written about endlessly, but this book actually covers new ground: his youth, education and early career. Just a glance at the cover -- not the inscrutable bearded face of textbooks and postage stamps, but a slim, young and handsome visage -- suggests how foreign this territory is. Here are the foundations of his evolutionary theories, including his fabled five-year voyage around the world aboard the Beagle. But most telling, here is the person who is becoming Charles Darwin.

Keith Thomson is an assiduous scholar and an absorbing writer, so this book is a fascinating read. He won me immediately by noting that since the Darwin men had a limited number of first names ("Charles" and "Erasmus" mostly), they were known in the family by nicknames. So Charles Robert Darwin, the fearsome intellect and alarming revolutionary, was called Bobby.

Bobby's career was hardly a straight line to evolution, even though his famous grandfather (Erasmus Darwin) proposed the basic idea. He studied first to be a doctor, then a clergyman. He was an amateur naturalist who acquired his first fame in geology, which was the first field to offer evidence of change over vast lengths of time, beyond the current Biblical interpretations.

He also fudged a lot of his early life in his own autobiography, and was notoriously lax in giving others due credit -- even though one of his first discoveries was stolen by a friend and mentor. Despite his independent income, he worried about his career.

Thomson also provides a captivating guide to a unique time, when sciences like geology and the life sciences were really just getting started, and enthusiastic amateurs made real contributions. (For much of Darwin's life, there was no such word as "scientist.")

This book solves the so-called mystery of why there was so much time between Darwin's voyage on the Beagle and publication of his theory: It took that long to work it all out. Proposing a mechanism for what was supposed to be the work of the Creator required mental adjustments as well as much supporting evidence.

Those theories remain essential to a lot of science and how we see the world, yet interpretations of them are still changing. "Darwin had the luck," said George Bernard Shaw, "to please anybody with an axe to grind." But now with this enlightening book there is a new account of Darwin's own evolution.