On that trip I was looking at my phone a lot—too much, really, an embarrassing amount. I’d just met a man I thought I might be in love with. He was smart and nerdy in the best possible way, and also kind, thoughtful, and funny, and I could not stop texting him. And video chatting with him. And thinking about him. He’s my husband now. Thank you, Daniel Rutledge, for being my best friend and lover and all-around good man.

Writing the book was tougher than I expected it to be. I thought at first that the story was going to be this light and funny examination of teenage sexual awakening. Then I got Ada on the page, and with Ada came these two sisters, and her brilliant whirlwind mother, and her bedrock father figure, and before I knew it, I was basically writing a family drama with the funny sex stuff as more of a side note. And during the entire process, Jodi Meadows talked me through the ups and downs and offered her invaluable insights about plot, pacing, and the perils and joys of sisterhood. Thank you, Jodi. Words truly can’t express how thankful I am to have you as my friend and writing partner.

At one point I was feeling stuck, and I spent a few hours one Saturday reading the first several chapters out loud to Amy Yowell, my best friend since I was thirteen years old; Ben Yowell, her awesome husband; and Kathleen Yowell, their amazing daughter. They laughed so hard at every joke that I instantly felt my confidence return—maybe I could write this book about (eek!) sex and not fall flat on my face. Thank you, Amy, Ben, and Katie—my favorite! And hugs to Gwen, the younger daughter, even though she wasn’t there, because that would have been totally inappropriate. . . .

On that note, thank you, Allan, my brother, for the conversations we had about this book that probably made you wildly uncomfortable. And thank you, Will, my son, who had to endure the sudden onslaught of “the talk” when I was reading up on how teens approach this subject differently than they did when I was sixteen.

Thank you, Katherine Fausset, for your continued encouragement and sound advice as my agent for almost sixteen years now. You’re the very best. A big thank-you also to the people at Curtis Brown: Holly Frederick, my film agent, and Sarah Gerton, especially.

Thank you, Erica Sussman and Stephanie Stein, my editors, for all the work you do to make my books as good as they can be. I’d also like to thank the entire team at HarperTeen and everyone who contributed to the book’s production: Alexandra Rakaczki, Jaime Herbeck, Louisa Currigan, Jessie Gang, Jenna Stempel-Lobell, Kristen Eckhardt, Sabrina Abballe, and Anna Bernard; Helen Crawford White, the amazing cover artist; and Joy Osmanski, the narrator of the audiobook.