Mark J. Flowers has pulled off something truly clever with Opportunity Cost and the Mystery of the Left Socks Lost — a whimsical, witty detective story that sneaks in a foundational economic concept without ever feeling like a lesson. At the heart of the mystery is Abigail Alexis, a young girl with big brains, a sharp eye for clues, and a knack for turning everyday chaos into opportunity (and a few dollars).

The premise is hilarious and instantly relatable: where do all those missing socks go? As Abigail launches her sock-investigation business, readers are gently introduced to the idea of opportunity cost — the trade-offs we make when we choose one thing over another. But rather than deliver a dry definition, the story brings the concept to life through smart dialogue, funny scenarios, and a plot that moves with energy and purpose.

The twist? Let’s just say it involves a very unexpected sock thief — and a satisfying resolution that ties everything together (pun fully intended). The illustrations are vibrant and full of character, with little visual jokes that kids will love to spot. Abigail herself is a standout: determined, curious, and a role model for problem-solving with purpose.

Best of all, this is a book that doesn’t underestimate its young readers. It trusts them to understand big ideas, and even more importantly, to enjoy them. A fantastic choice for classrooms, bedtime, or any curious kid with a missing sock and a million questions.

Opportunity Cost and the Mystery of the Left Socks Lost is such a clever and fun way to introduce economic thinking to kids. The story follows Abigail Alexis on her sock-sleuthing adventure, blending humor and mystery with smart life lessons about decision-making and priorities. I really enjoyed how the book made a tricky concept like opportunity cost feel relatable and understandable without dumbing anything down. It’s the kind of educational book that actually makes learning feel like play.

A detective story and an economics lesson? Consider my socks knocked off. 🧦💨 This book is hilarious, smart, and full of fun energy—plus, Abigail Alexis is an absolute legend-in-the-making. She’s chasing missing socks, making tough choices, and dropping knowledge along the way. I totally wish I had this book as a kid (or, let’s be real, last week). Kids will laugh, learn, and maybe even start budgeting their allowance. Clue by clue, this one’s a winner. 🔎📚✨

Detective work meets dollars and sense in this fun-filled econ adventure!

Opportunity Cost has never been this adorable—Abigail’s sock-snatching sleuthing is clever, quirky, and the cutest way I’ve ever seen economics explained (and yes, I wish I had this book as a kid!).

I love how Abigail got the kids to search for their socks without them knowing that they were searching for it! I was also curios to know where the socks had gone and it was Jasper all along. I'm glad he learned his lesson and Abigail is a young entrepreneur! Omg, I didn't expected the twist at the end!

Thank you to Mark J. Flowers, Netgalley, and Modern Sense Publishing for a copy of this book in exchange for an honest review. Someone is stealing socks. Abigail sets out to find the culprit and earn some money. This book is adorable. The illustration is amazing and a children's author I would read again!