I downloaded the sample from the the (US) Kindle store yesterday. I noticed the price was $2.39.
Today, I went back to the store to purchase the book, but the price had gone up to $9.99. At that price, I hesitated.
Then, while perusing the UK Kindle store, I noticed the book listed there at £1.39, which is approx $2.15 (US). So I grabbed it from there.
It seems surprising that (i) the price can change so quickly; and (ii) it is so much cheaper in the UK, given that it is an American book, and also the UK price includes VAT.
Never mind. It's not the first time I've seen things like that. Anyway, I'm looking forward to reading it.