Why series fall apart on real shelves
Series rarely break in one go. You read the first three Discworld novels from the library, buy the fourth secondhand, and a friend gives you the eighth for your birthday. The Jack Reacher paperbacks picked up at airport bookstalls end up in two different rooms. One Outlander volume is lent out and never comes back. A few years later you stand in front of the shelf and can't say whether book five is missing or just sitting in the bedroom. The more volumes a series has, and the longer you take to read it, the more gaps appear. If you want to track missing books in a series, you need something that remembers the whole run, not only the copies you happen to see.






