Infinite Powers

You might like Infinite Powers (Steven Strogatz) and Faraday, Maxwell, and The Electromagnetic Field (Nancy Forbes)

I suggest Infinite Powers by Steven Strogatz. It doesn't matter if they already took a calculus course, I guarantee it's a much better way to make them appreciate the the subject than any textbook. And if they don't know calculus yet, that just makes it even better! If I'd read this book as a teenager, maybe I would've passed Calc I on my first try as opposed to my third. With a C-.