Paris - Everyone bar a saint can recall being curt with a supermarket checkout girl at some point, but after reading a new best-selling book in France, many a customer might think twice about being unfriendly to the woman behind the counter.

In her book "Les tribulations d'une caissiere" (The Trials of a Checkout Girl) Anna Sam, 28, dissects typical supermarket users, including many familiar types. Her critical eye registers the notorious moaners and the bargain hunters along with the shop-until- you-drop types and of course, the pleasant customers who do mind their manners. The book has already sold 100,000 copies in France and is set to be published in English later this year.

Since the hilarious memoir appeared in France, the number of people being self-consciously friendly and polite at the cash till has apparently increased: "I get lots of e-mails and letters from customers who thank me for having opened their eyes to what it is like," Sam told Deutsche Presse-Agentur dpa.

Sam's 170-page book is aimed at potentially bad-tempered or impatient shoppers and she hopes that these will refrain in future from asking such inane questions as "Are you open?" to which the answer can only be: "I'm not, but the cash till is."

After finishing the book, famished customers who tuck into a tuna fish and mayonnaise sandwich before paying for it might think twice: "He munched his sandwich loudly, and with his mouth wedged so wide open that there was no need to read the list of ingredients on the wrapper," reads one passage in the book.

Sam worked part-time for eight years as a cashier at a large supermarket in the town of Rennes. The "stint" was initially intended to finance her literature studies. However, she could not find a better job on graduating: "And so I ended up becoming what is often referred to these days as a 'till-based customer service assistant'," she comments drily at the start of her book.

Anna Sam dealt with around 300 customers a day, said "thank you" roughly 500 times a day and scanned between 700 and 800 items an hour. She also lifted 800 kilos worth of goods per hour.

Using the pseudonym of Miss Pastouche, Sam began documenting her experiences anonymously in an internet blog in April 2007. She advanced to become France's best-known supermarket cashier and a spokeswoman for fellow sufferers. So what inspired her weblog?

"I noticed that checkout staff had a strong urge to communicate with each other and since I'm able to express myself better through writing better than I can through talking, I came up with the idea for a blog," said Sam.

Success was not long in coming - The French-language blog http://caissierenofutur.over-blog.com/ has been clicked on more than a million times and has attracted thousands of contributors. Today, it is a cult website in France.

The collection of anecdotes and customer experiences by the young writer was soon a best-seller and a second book is being prepared since "there is so much more to say about working in a supermarket," says the author.

Despite the wit, the book conveys a serious message about how customers treat other people, even if one or two of the examples quoted seem a little forced and banal - such as when Sam observes: "I assume the bargain-hunter was a good cook - for how could she otherwise combine tinned sardines, cheese-flavoured chips, coffee and tomato sauce? That kind of culinary balancing act is not easy." (dpa)