Fun story. Someone who lived at my address in NYC worked for the NYTBR and we still get pre-release books from publishers several times a year. We tried to contact this person, NYT, no one cares. So, I open them, read the cover letter, and put them out on the side walk with a note, "Free".
I dont think I have ever seen numbers on any of these "books", they often don't have covers... I imagine some of them if reviewed poorly may never even make it to market.