Madame L is not reviewing a book about the Amazon, but rather the online book-and-everything-buying service she often recommends, Amazon.com.
As you may be aware, Amazon uses what it likes to call a "dynamic" price system, in which the price you're being charged for an item may change over time---and sometimes over the amount of time it takes to look up an item and put it in your shopping cart.
You may think of this as a bait-and-switch tactic---Madame L certainly does!---but it's legal. According to this consumer advocate, "Not only do prices move up and down on a regular basis, but also they're often adjusted based on exactly which customer is mulling a purchase. The practice, called price customization or dynamic pricing, weighs factors as it sets prices such as a customer's income, buying habits, or the popularity of an item on a given day."
The Romans said it best: "Caveat emptor." If it happens to you, you should contact Amazon.com to complain, but be prepared to be persistent.
Although she has had problems with this in the past, Madame L has complained about it, with the result that it hasn't happened to her since then. She continues to use Amazon.com, but very carefully; and hopes all of you Dear Gentle Readers will use care, too.
Also, please share with Madame L any "dynamic price" experiences you've had with Amazon.com and any other retailers.