Royal bastards - Andrew Shvarts

Tilla's father loved her as a child, but cast her aside when he had trueborn children. She spends her days exploring long-forgotten tunnels under the castle and nights drinking with the servants. Tilla longs to sit by her father's side, instead she sits with the other bastards. Then, at a feast honoring a visiting princess, the royal shocks everyone by choosing to sit at the Bastards' Table. Before she knows it, Tilla is leading the princess on a late-night escapade. But rebellion is brewing - the bastards band together and flee, realizing only they have the power to prevent civil war.