SISTER, by Rosamund Lupton (Crown, $24.) In Lupton's novel, which is both tear-jerking and spine-tingling, a free-spirited sister's death -- perhaps it was murder -- forces a highly conventional woman to examine the truth of their relationship. ANDES, by Michael Jacobs (Counterpoint, paper, $24.95.) Jacobs, a somewhat unlikely adventurer, describes his trek down South America's great mountain range to its icy finish in Patagonia. [ABSTRACT FROM PUBLISHER]