Nine Man Tree — Robert Newton Peck

Deep in the Florida swampland, young Yoolee Tharp is fast becoming a man.  His ongoing mission is to protect his little sister, Havilah, and his mother, Ruth Ann, from the violent rages of his hard-drinking father, Velmer.

Then another unspeakable horror enters the Tharps' lives when their tiny Everglades settlement is stalked by an enormous killer beast. When Yoolee's father disappears, it's up to Yoolee to protect his family once again, aided only by his wits and courage--and a mysterious stranger.