This is one of those books that's considered a 20th century classic, but that most people haven't gotten round to reading. From Amazon:
"Here is the book that transformed a generation: an unforgettable narration of a summer motorcycle trip across America's Northwest, undertaken by a father and his young son. A story of love and fear -- of growth, discovery, and acceptance -- that becomes a profound personal and philosophical odyssey into life's fundamental questions, this uniquely exhilarating modern classic is both touching and transcendent, resonant with the myriad confusions of existence . . . and the small, essential triumphs that propel us forward."
Since it's a classic, it's never gone out of print, and used bookstores will probably have a copy. There are also 6 copies available in the Ottawa Public Library, and of course e-versions are available.