In one of the most beautiful river valleys in Europe, in the region known as Périgord in southwest France, castles crown the hills, and the surrounding villages seem carved all of a piece out of the local stone. In 1985, in the shadow of one of these medieval castles, Betsy Draine and Michael Hinden fell in love with a small stone house that became their summer home.<BR>    Like any romance, this one has had its ups and downs, and Betsy and Michael chart its course in this delightful memoir. They offer an intimate glimpse of a region little known to Americans?the Dordogne valley, its castles and prehistoric art, its walking trails and earthy cuisine?and describe the charms and mishaps of setting up housekeeping thousands of miles from home.<BR>    Along with the region's terrain and culture, <I>A Castle in the Backyard</I> introduces us to the people of Périgord?the castle's proprietor, the village children, the gossipy real-estate agent, the rascally mason, and the ninety-year-old widow with a tale of heartbreak. A celebration of a place and its people, the book also reflects on the future of historic Périgord as tourism and development pose a challenge to its graceful way of life.