I just noticed at the Amazon site for Remembering Ruby that it is currently included in the "4 For 3" promotion. That means that if you buy four items that are eligible, you'll get the least expensive one for free.
I know nothing about this promotion as far as how long it is going to go on, but more details are at the Amazon site.
So, if you want to stock up for gifts, get four books! Otherwise, if you only want one, find three other items included in the promotion and you can save money that way, too!