All human beings, says an African legend, have an animal double. Some doubles are benign, others wicked. This legend comes to life in Alain Mabanckou’s outlandish, surreal, and charmingly nonchalant Memoirs of a Porcupine. When Kibandi, a boy living in a Congolese village, reaches the age of 11, his father takes him out into the night and forces him to drink a vile liquid from a jar that has be...