Homegoing is a daring and ambitious debut. Make note of Gyasi's name, because with this novel she has laid the groundwork for an illustrious writing career.
She begins her story with two half-sisters, Effia and Esi, who never meet. Each subsequent chapter follows someone from the next generation in the family line. The half-sisters are born in Ghana, but their lineages diverge immediately, with one sister remaining in Ghana, married to a white slave trader, and the other captured and sent on a slave ship to North America.
Because each chapter deals with a new character in a new generation, the books feels more like a series of linked short stories or vignettes than a long, sweeping novel—a choice which keeps the novel to a manageable length and prevents it from bogging down with detail. It's a lot to process, but it's not so demanding that it would monopolize your whole summer.
A few other good books that tell stories of families through several generations:
The Children's Crusade by Ann Packer
Green Island by Shawna Yang Ryan
The Turner House by Angela Flournoy