The Song of Achilles

Greece in the age of heroes. Patroclus, an awkward young prince, has been exiled to the court of King Peleus and his perfect son Achilles. By all rights their paths should never cross, but Achilles takes the shamed prince as his friend, and as they grow into young men skilled in the arts of war and medicine their bond blossoms into something deeper - despite the displeasure of Achilles' mother Thetis, a cruel sea goddess. But then word comes that Helen of Sparta has been kidnapped. Torn between love and fear for his friend, Patroclus journeys with Achilles to Troy, little knowing that the years that follow will test everything they hold dear.
(from goodreads.com)