When it was published in 2016, Yaa Gyasi’s first novel Homegoing was lauded for its broad historical, geographical, and generational sweep, tracing a sprawling family tree back to two half-sisters in 18th-century Ghana. Transcendent Kingdom (Knopf, September) also explores the Ghanaian-American immigrant experience, this time through the eyes of a neuroscientist named Gifty, who turns to a discipline called optogenetics to make sense of family tragedies and an upbringing immersed in the racism and evangelism of the American South.