They are part of the Amazon group. A place for second hand bookshops to advertise their stock.
Yes they do ha e some good prices but also some high ones, I looked for 500 wooden bowls on it and the price was very high. The well known auction site had it for a reasonable amount, so it pays to compare them both before buying.
Another to look at is the online Oxfam shop, they also have quite a wide range of books, sometimes about wood turning, but they set their prices against the 2 above mentioned.