From Kathy Twitchell, librarian at Literary Lantern Bearers in Kingfield, Maine.
PAGE QUALITY: Just a quick note about pages. The whiter (or creamier) the paper, the less lignin content remains. Lignins naturally occur in plant and wood fibers. The oxidation of these lignins is what makes cheap paper break down over time, yellowing and becoming brittle. A higher grade paper has far less lignin and won’t deteriorate quickly, but it is more expensive to produce. (This is why a photocopy of a newspaper article will last far longer than the newspaper on which it was originally printed.)
Most often paperbacks (and turtlebacks) use a lower quality, darker toned grade of paper, so they tend to rapidly age. Sometimes, though, hardcover editions are also made with a lower grade paper. I have seen this in some book club editions, and also in many books printed during WWII. Those “wartime editions” frequently contain a note about being made in adherence to publishing restrictions imposed by the American government during the war.
Some popular children’s series published in the years 1920-1960 (or so) contain some hardcover editions with a lower quality of paper. I have seen this with some Nancy Drew and, I think, The Bobbsey Twins? If I’m looking at duplicates within such a series, I choose the copies with the white or cream colored pages, as opposed to gray or yellow. This discrepancy in paper is what led to the phrase “pulp fiction” in adult publications. https://www.dictionary.com/browse/pulp-fiction
Let’s examine yet another complication. Modern paperback reprints, particularly from our beloved small publishers, are most often released with a very high quality paper. Because of the trend in more recent years to employ a glued hardcover binding instead of a sewn one, in many cases a good quality paperback can last longer than a poor quality hardcover edition. The flexible cover is less likely to have the page block fall out!