Susanna Moodie and Catharine Traill, English-born sisters, came to Canada with high expectations. These hopes were not fulfilled, but Moodie and Traill adapted to their new home and, in time, produced work that would help shape the nation's literary culture. The sisters arrived in what were then the wilds of Ontario in 1834, their husbands having assured them that, by virtue of their education and background, they would immediately be welcomed as members of the ruling elite. They instead found themselves ''stuck in the backwoods,'' where free land was to be had. But though at first both complained vigorously and often and developed what Northrop Frye called a ''garrison mentality,'' they eventually adjusted to frontier life and its many hardships and sorrows, from subfreezing temperatures to the death of children. Their difficulties were not eased by their husbands' evident inability to earn or keep money, and, though well received, their early writings about life on the edge of the wilderness--Susanna's poems and sketches, Catharine's book The Backwoods of Canada--did not earn much money either. But, as Charlotte Gray deftly documents, the sisters kept at it, producing now-classic works such as Roughing It in the Bush and Life in the Clearings and earning considerable fame throughout the English-speaking world. ''Until I decided to write this double biography,'' writes Gray, ''I had not noticed how often Susanna and Catharine appear in the fiction and non-fiction of contemporary Canadian writers. More than just Canadian literary archetypes, they haunt our collective imagination.'' Gray's graceful biography crowns the huge library devoted to the sisters, and it makes a fine companion for readers now discovering their work and contributions. --Gregory McNamee