Well, this is purely anecdata, but one of the municipal library systems in my region has a catalogue that shows the usage numbers for each copy of a particular book, as well as last loan date, etc.
So if you were to go in and check the hardcover edition of Dan Brown's The Da Vinci Code via the
catalogue link at the top of their website, you'd see that they had 19 copies, almost all with a minimum usage of 30+ loans, and the top 3 circulating copies at 60+ loans.
Also, half their copies are going unused at the moment. I suspect you'd get much the same numbers for many of the popular bestsellers of yesteryear, and even higher usage numbers for certain perennial classics.
If you check the oldest copy of Agatha Christie's After the Funeral, there are 3 copies at 78, 69, and 42 uses respectively, and all of them checked out as recently as this year.