What is also of interest are the impression dates: one can trace the popularity of the book, especially if one knows the size of the print runs and the names of the printers. If there are two impressions [printings] in the same year, especially by two different printers, (barring disasters) you know the book is popular.
My particular interest is the early Ballantine LOTR paperbacks (and variations among same). The early Ballantines listed both printing [impression] year and month. (This was later discontinued.) One can see the explosion of interest in the books, with even two printings in the same month! I believe it was printed in both the USA and Canada. The late Dr. Richard Blackwelder tried to collect every printing of the Ballantine LOTR: for those who are interested, they're in the Marquette archives. I think Hammond & Scull studied them.