This book is part history and part philosophy of arithmetic. He also includes a few exercises in italics (one every few pages).
I love his easygoing tone
(arithmetic is not mathematics, it's an art or craft, something like
knitting, I enjoy it, and I hope you will), his low-key sense of humor, and his perspective.
I loved his book
Measurement, and look forward to someday working through all the
challenging problems in it. This one is much easier, and yet it's not boring for
me.
It would be a lovely book to read to kids and think through together.
(It came out this year in hardcover. $22.95. I love the cover, though I know I shouldn't judge a book by that...)
[Edited to add:
I wrote this review before finishing the book, because I was so excited. I've read a few more pages now. Sadly, Lockhart is sometimes sexist. On page 45 he mentions the (Japanese) emperor's concubines, and says "Now, this is why people do arithmetic!" (To please the concubines.) No. It's not. And I thought better of you, Paul Lockhart.