Greenwode - The Books of the Wode, #1

Daring the old gods. Defying the new. The making of a legend-and a truly innovative re-imagining of Robin Hood. When Rob of Loxley finds an injured nobleman's son in the forest, neither he nor his sister Marion understand what befriending young Gamelyn could mean for the future of their beliefs. Already the ancient spirits of the Old Religion are fading beneath the iron of nobleman's politics and the stones of church subjugation.
More, the druid elders warn that Rob and Gamelyn are cast as sworn adversaries, locked in timeless and symbolic struggle for the greenwood's Maiden. Instead, in a theological twist only a stroppy dissident could envision, Rob swears he'll defend the sacred woodland of the Horned God and Lady Huntress to his last breath if his god will let him be lover, not rival, to the one fated as his enemy. But in the eyes of Gamelyn's Church, sodomy is evil...
and the old pagan beliefs must be subjugated-or vanquished