I've seen people in various places get confused about this, so here's a factoid:

If you see a book being sold on the '3 for the price of 2' table, that doesn't mean it's doing badly. It's doing well.

It's not uncommon for people to assume that 3-for-2 means that the bookshops have far too many copies that nobody wants and are trying to shift them any way they can. Actually, it means they're anticipating selling so many copies that they can sell them at a discount and still clear a decent profit. It means that these books are the star attractions of the month. The 3-for-2 table is a good place for your book to go, because what it means, above all, is that people will see it. Almost anyone looking for something will drift over to that table, and a book that's on display that prominently stands a much better chance than a book that's just tucked away on the shelf. Books generally only sell 3-for-2 for a month or so, so the hope is that lots of people will buy it during that time, but also that others will see it during that time and then buy it later. If you're on that table, it's good news: I had a month there, and had to keep explaining to people who commiserated me that I was actually delighted.

What people are confusing it with is remaindering. Remaindering is bad, bad news for a book. At best, it means that it's come out in a new edition and they're selling off the old ones. More seriously, it means that sales of the book have slowed down so badly that it's not worth keeping it around any more. The publisher decides not to print or promote any more copies, and sells off the rest at a knock-down price to clear warehouse space. A book that's being remaindered is on its way to going out of print.

So next time you see your favourite author on the 3-for-2 table, don't feel bad for them. They're grinning.