We wondered what Caroline Alexander has been up to since her phenomenally successful The Endurance. The Bounty is a brilliant choice. She tackles William Bligh, Christian Fletcher and the story of the Bounty with the same spirit and meticulous research. Hers is a rousing tale of class barriers, the British courts and remarkable seamanship. And her Bligh is a far cry from that portrayed by Charles Laughton. The man may have been prickly (and from working class roots, which she argues was his real crime) but Bligh was a remarkable navigator. With maps and 32 pages of illustrations.  (PAC134, $17.00)