C.J. Box has never lacked in talent for writing rugged frontier-type heroes, like Joe Pickett and Nate Romanowski, who’ve helped define the post-modern Western. His Cassie Dewell character is all that and more, as is firmly on display in "The Bitterroots" (Minotaur, $27.95, 320 pages).No longer a cop, Dewell is now working as a private investigator to, in part anyway, enjoy the rigors of being her own boss.