By Nelson Mandela and Mandla Langa. It has been four years since Nelson Mandela died and 19 since he began chronicling his tenure as South Africa's first democratically elected and first black president. Writer Mandla Langa has worked with Mandela's unfinished manuscript to complete Dare Not Linger, a sequel to 1994's Long Walk to Freedom. Dare Not Linger is not the sort of book you can swallow in one gulp, so don't be in a hurry. In an interview, Langa said he wants the book to help South Africans remember when "we held the moral high ground, when we walked with our heads held high." The book's title is taken from the final few paragraphs of Long Walk, where Mandela writes: "I can rest only for a moment, for with freedom comes responsibilities, and I dare not linger, for my long walk is not ended." A warning, perhaps, to South Africa's future leaders not to forget what it took to jettison colonialism and apartheid and build a nation based on equality. Farrar, Straus and Giroux (2017), English, 384 pages.