As a graduate student in Laramie, Wyo., in the 1990s, Sarah Mentock spent many weekends hunting for bargains at neighborhood yard sales. On one of those weekends, she spotted “The Lord of the Isles,” ...

Ever wonder if that dusty old book on your shelf might be worth a small fortune? From rare first editions to long-forgotten limited prints, valuable old books might be hidden in your attic or a thrift ...