The Awakening by Nora Roberts

#1 New York Times bestselling author Nora Roberts begins a new trilogy of adventure, romance, and magick in The Awakening.
In the realm of Talamh, a teenage warrior named Keegan emerges from a lake holding a sword—representing both power and the terrifying responsibility to protect the Fey. In another realm known as Philadelphia, a young woman has just discovered she possesses a treasure of her own...
When Breen Kelly was a girl, her father would tell her stories of magical places. Now she's an anxious twentysomething mired in student debt and working a job she hates. But one day she stumbles upon a shocking discovery: her mother has been hiding an investment account in her name. It has been funded by her long-lost father—and it's worth nearly four million dollars.
This newfound fortune would be life-changing for anyone. But little does Breen know that when she uses some of the money to journey to Ireland, it will unlock mysteries she couldn't have imagined. Here, she will begin to understand why she kept seeing that silver-haired, elusive man, why she imagined his voice in her head saying Come home, Breen Siobhan. It's time you came home. Why she dreamed of dragons. And where her true destiny lies—through a portal in Galway that takes her to a land of faeries and mermaids, to a man named Keegan, and to the courage in her own heart that will guide her through a powerful, dangerous destiny...