Clare is a pretty typical teenager. She's smart but kind of a slacker. She's outgoing but a little insecure. She's not a trouble maker, but trouble seems to follow her. She also has a centuries-old Druid blood curse running through her veins.Now, with a single act done without thinking about it first, what started off as a boring summer suddenly spirals into a deadly race to find a stolen artifact, avert an explosive catastrophe, save a Celtic warrior princess, right a wrong that occurred centuries before Clare was born, and maybe, if there's still time left, get a date.It's the kind of adventure that happens to a girl once every... never.What I love about Lesley's writing is how much she blends magic and absolute excitement and enjoyment. With all the weird, complex, Druid- & Celtic-related events that happen to Clare, there's still laughter and fun. Most of that comes from Clare and her slightly snarky attitude, her friend Allie with her smarts and nerd knowledge, and Milo, Al's cousin, another nerd but also, in the eyes of Clare, really really good-looking. I'm starting to notice a few more hot nerd guys popping up in books.This book reminds me of a magical British-Celtic-Druid version of Myra McEntire's Hourglass. Weird time travel, the dangers of changing history, someone wanting to manipulate our fair heroine and her abilities, said fair heroine thinking she's possibly insane then accepting it when she has to fix a giant problem.Clare is one of the most enjoyable parts of this book. Her attitude is so familiar and teenager-like. She's got a high IQ, but she almost doesn't care and just wants to be normal. She'll sort of pay attention to things, but not when it's scholarly and she's on summer vacation. Unless she's totally wrapped up in this ancient Celtic situation and starts to pay attention because her life depends on it. The snark is perfect, it provides moments of light and laughter in dark and brutal times.The second enjoyable part of the book is the history. There are some days when I wish my degree was in history, specifically British history, and not in English lit. The history is so magical, so realistic, so moving and powerful, it makes you forget that those events happened almost two thousand years ago. Sure, there have been tweaks and changes made by the author, but the root of the story still exists, back in a time where the Celts were at war with the Romans and blood magic was commonplace.Once Every Never swept me up in its blood magic spell and shoved me straight back into Britain's past. I can't begin to describe how much fun this book was to read. So much fun. Thank you, Lesley, for feeding the sci-fi and history nerd living inside my head.