Broad principles are easy enough to decide: fiction separate from non-fiction and alphabetised by author; non-fiction broken into a handful of categories. But then come the hard questions. Japanese fiction in the fiction or the Japan section? (Fiction for the moment). Hardbacks and paperbacks mixed together? (Yes for fiction, since not many hardbacks; no for politics/history/biography where hardbacks predominate). And there will always be anomalies that will plague your mind as you lie in bed: “Should I really put the two paperback volumes of the Teddy Roosevelt biography with the hardback one?” It’s a wonder I sleep at all.
Tiny minority they may be, but I am on friendly terms with several people who otherwise show all the signs of being decent, intelligent human beings but have no system at all for filing their books, other than to toss them up there in vaguely the order they were bought or read, perhaps adjusting slightly for size. Yes, my perseverance with such friendships does indeed demonstrate my generosity of spirit.
These people no doubt do something similar with their e-books, but those at least are out of sight. For the rest of us, Kindles merely remove from public view the chosen solution but make the choice little easier. Yet while e-books do not help with the question of where to file finished reading material, it seems to me that perhaps their greatest merit – greater even than convenience or cost – is that they prevent that most heinous of crimes: the sorting of books by colour.