Readers whose mental image of neurologist and prolific author Oliver Sacks is defined by his avuncular, white-bearded visage may be puzzled, at first, by the photograph of the buff, leather-jacketed young man astride a motorcycle that graces the cover of his memoir, ON THE MOVE. If they are, it should only take a few pages of this engrossing autobiography to understand why that image captures perfectly the spirit of his peripatetic and relentlessly curious life.

Considering that both of his parents and two older brothers were physicians, it's hardly surprising that Sacks gave little thought to any career other than medicine. Almost from the beginning, that career, most of which he pursued in the United States after leaving his native England for Canada in 1960, was driven as much by the storytelling impulse as it was by an affinity for science. Admitting his frustration at the tunnel vision of his residency training at UCLA in the 1960s, because "I think in narrative and historical terms," Sacks soon abandoned the laboratory for clinical practice.

"...engrossing... What gives this memoir a unique poignancy is the knowledge that Sacks was diagnosed earlier this year with terminal liver cancer."

Sacks ties his account of the highs and lows of that practice to many of his 12 previous books, including AWAKENINGS, the story of the transformation of postencephalitic patients treated with L-dopa that was made into the movie starring Robin Williams and Robert De Niro, and THE MAN WHO MISTOOK HIS WIFE FOR A HAT (the 1985 book that brought him to prominence). Though he's never bitter in describing it, Sacks understands that his professional recognition has not matched the regard in which he's held as a popularizer of knowledge about disorders as diverse as Tourette's syndrome and color blindness.

Sacks also frankly describes how his sexual orientation has shaped his life, despite enduring more than 35 years of celibacy after the end of a relationship in 1973. When he revealed to his parents that he was gay, shortly before he left for Oxford in 1951 (at a time when homosexual acts were punishable as crimes in England), his mother reacted with horror to what she called this "abomination."

As the cover photograph suggests, Sacks has had a lifelong passion for motorcycles, despite abandoning them in the early 1970s when he grew tired of contending with New York City traffic. When he lived in Southern California, it was not uncommon for him to embark on long weekend rides to the Grand Canyon or the Mojave Desert. He celebrated passing his medical boards and getting his green card (he's never secured United States citizenship) with a two-month, 8,000-mile jaunt around the United States, some of whose highlights are captured here in the form of contemporaneous journal entries.

But as much as Sacks delights in sharing the parts of his fully engaged life that have brought him pleasure, he doesn't shrink from describing some of the less attractive aspects of his past. In the 1960s he struggled with an amphetamine addiction. He also admits he overindulged in weightlifting, securing for him the California record for squat lifting 600 pounds when he was part of the scene at Venice's Muscle Beach during that decade, but leaving him with the painful residue of his extreme workout regimen. One of his most profound regrets is his inability to do more for his brother, Michael, afflicted with schizophrenia from age 15.

Throughout his life, Sacks has been sustained as much as anything by his writing. He even confesses to recording his observations about a color blind patient, an artist, while attending a performance of Mozart's Mass in C Minor. "The act of writing is an integral part of my mental life; ideas emerge, are shaped, in the act of writing," he says. He displays that gift generously in this book, effortlessly blending accounts of his medical cases with revealing and entertaining stories of the people --- among them poets W.H. Auden and Thom Gunn and Israeli diplomat and historian Abba (known to him as Aubrey) Eban, a first cousin --- whose lives intersected his.

What gives this memoir a unique poignancy is the knowledge that Sacks was diagnosed earlier this year with terminal liver cancer. In a February New York Times essay, he described his desire to live out whatever time remains to him in the "richest, deepest, most productive way I can." Reflecting, in that piece, on the life he chronicles in ON THE MOVE, he wrote, "I have loved and been loved; I have been given much and I have given something in return; I have read and traveled and thought and written. I have had an intercourse with the world, the special intercourse of writers and readers." That's an apt and moving summary of the fascinating and productive life story he shares in this book.