The Song of Achilles by Madeline Miller

When word comes that Helen of Sparta has been kidnapped, the men of Greece, bound by blood and oath, must lay siege to Troy in her name. Seduced by the promise of a glorious destiny, Achilles joins their cause, and torn between love and fear for his friend, Patroclus follows. Little do they know that the Fates will test them both as never before and demand a terrible sacrifice.