Amazon UK:
Ill Met by Moonlight by Sarah A. Hoyt is just £0.99.
Originally published by Ace Books back in 2001, this is her own ebook edition.
"Young Will Shakespeare is a humble school master who arrives home to find his wife and infant daughter, Susannah are missing, kidnapped by the fairies of Arden Woods, the children of Titania and Oberon. His attempts at rescue are interrupted and complicated by a feud over throne of fairyland, between Sylvanus, king regnant, and his younger brother Quicksilver who is both more and less than he seems. Amid treachery, murder, duel and seduction, Shakespeare discovers the enchantment of fairyland, which will always remain with him, for good and ill."