It was the 1990s, and Pop-Pop was dying. Pop-Pop was my grandfather, wrestling with late-stage diabetes, and he didn't have long to live. This news hit me hard; I'd appointed him years earlier as the Good Guy Role Model in my life when my adoptive father absented himself from that position. I needed to go home and see him one last time. Whoever Sylvan Bernard Gordon had been to anyone else in his life, he taught me the value of shared, companionable silence riding next to him in the car, his easy-listening radio station lulling us with elevator music. He was the grocery shopper and salad-preparer in his household, normalizing for me that men could choose to do those things in a family. He never did convince me to enjoy golf, though I would watch it with him just so we could hang out more. What I didn't know then was how he was about to indirectly lead me on an unexpected journey – one that took decades to come to light in my new book, The Only Song Worth Singing. When I got the news from mom – Pop-Pop's daughter – I was a junior at Boston University. I was taking a class with Nobel Peace Prize-winning author Elie Wiesel about folk tales around the world, and thought, I could read Jewish folk tales to Pop-Pop while he rests. Pop-Pop was the most religious person in my immediate family; most of us were culturally Jewish, and I was still years away from learning about my biological family's Irish heritage. Alas, there was nothing of note in the school library's folklore section about Jewish folk tales. But next to the "J" section was the "I" section – and my fingers landed on Irish Fairy and Folk Tales. I did a double-take on the author's name: W.B. Yeats. Yes, the same Nobel Prize-winning poet who gave us "The Second Coming" with its indelible phrases like "things fall apart; the center cannot hold" and "what rough beast, its hour come round at last, slouches toward Bethlehem to be born." I grabbed the book and devoured it. Of course, I already knew some piecemeal Irish folklore: Green is important! Leprechauns on cereal boxes! Ghostly banshees! Fluttery fairies like Tinkerbell! But Yeats' book, a combination of stories collected from his travels around Ireland in the late 1800s, poetry and rough cataloging of the mythic creatures into groups like The Trooping Fairies and The Solitary Fairies, put them in their proper context for me. Irish fairy tales were not sanitized like the Disney versions of the Grimm ones I'd grown up reading. Irish fae were capricious, mischievous and sometimes downright mean. Good deeds were not necessarily rewarded; some folk got punished for ignoring rules they didn't know existed. There was complexity, depth and randomness. Strangely, these fae folk felt more real because of it. Yeats’ Irish folklore in a proper context spoke to me. I learned there was a whole language called Irish. I learned a leprechaun (or, per Yeats, lepracaun or even leith bhrogan) was a fairy shoemaker. Yeats included a musical transcription of the banshee (bean sídhe) cry, quaintly crediting "Mr. and Mrs. S.C. Hall" for the wail that signals death. Then I stumbled on Yeats' description of the leanhaun shee (as he wrote it; other spellings of the creature vary). She was the fairy mistress, the "Gaelic muse" who "gives inspiration to those she persecutes." She's the reason the "Gaelic poets die young." Talk about a lightbulb moment. I was obsessed with music, and the idea of our modern poets — rock stars — paired with an ancient muse-meets-vampire flipped all my switches. I'd never written fantasy before this. I just knew this was the book I had to write. And that book is The Only Song Worth Singing. It's been with me for decades, through countless rewrites and my growing maturity as an author. It landed me an agent 10 years ago, and now, at long last, I get to introduce musicians Mal, Ciaran and Patrick – and my scary fairies Caitlin and Sheerie – to the world. And I wouldn't have gotten there without a trip to the library for my grandfather and an encounter with an iconic Irish poet. Some critics take issue with Yeats’ methodology in collecting his stories. As a member of the Irish gentry, the poorer folk might have been willing to tell him whatever he wanted to hear. Others suggest the poet may have invented the concept of the leanhaun shee altogether, and (This last bit gets some airing in The Only Song, too.) I didn't know I had Irish ancestry when I started The Only Song Worth Singing, or when Yeats’ book gave me and my grandfather solace in his dying days. But like the cry of the banshee, it called to me. The PEOPLE Puzzler crossword is here! How quickly can you solve it? Play now! That's why I've dedicated this book to my grandfather, a man whose first name – Sylvan – suggests greenery, forests and wild places. Maybe it's magical thinking, but I like to imagine that the final thing he taught me was the way down this path, to this place, to this story. Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer , from celebrity news to compelling human interest stories. The Only Song Worth Singing comes out April 8 and is available for preorder now, wherever books are sold.