I now warn people off booking.com after a really bad experience with them three months ago. I had used them for a large number of bookings for several years, but they treated me very badly and there seems no way of escalating things to a higher level. So I walked. Still use them to find hotels, but then use another engine to actually book, or book direct with the hotel.
hotels.com seems to be just as good if you need a booking engine.
I am told that booking.com charges hotels and apartments a commission of 19%, so it is often better for the hotel or apartment if you book direct and then you can negotiate a lower price while the hotel still makes more money than they would have done.
Actually that sounds like my experience with
The Westin Wall Centre, Vancouver Airport Hotel which was the hotel that replaced the problem I had with Booking.com when I went to Vancouver last trip.
I found a rate on hotels.com and phoned Westin directly and they matched the price that hotels.com gave me. And I get points from it so better for all us.