Thoughts on what makes books "unputdownable." The trifecta of efficient plotting, occasional lyric prose or deft imagery, and engaging characterization seems a fair summary.
My mind snagged, though, on the division of books as either conducive to fast reading or to contemplative reading. The latter is not quite the same as being elliptical or something you can dip in and out of. Certain books are elliptical and strange and episodic, in a way that might make them ideal candidates for the sort of on-again-off-again reading that Bachner enjoys,* but may also be "unputdownable": you can blow through the interludes and meditations in great gulps, even in a single night, because something (maybe not the plot, but some current of desire) draws you in and refuses to let you surface. (Bachner seems drawn to books that almost force you to surface; this is, as she recognizes toward the essay's end, almost a guarantee of reduced readership. Some people will not enjoy being pushed out, and some may never return.**)
This is the sort of thing I think about a lot, without actually teasing out the components, when looking for travel reading. The ideal travel book for a beach trip is either fast reading or entirely episodic; the former is effortlessly immersive, and many of us don't want to have to work hard at getting into a book on a lazy vacation. The latter has its own appeal in this situation, as you may be reading in small chunks of time, while you sunbathe or between bursts of activity. Something that does not require sustained attention or recall of what's previously read, like a volume of short stories, may fill these gaps ideally.
A book that is unputdownable may actually interfere with one's plans, such as they are. Perhaps the appeal of trashy "beach reads" can be said to rely in part on their low status; despite our emotional need to continue reading, we're aware that doing so is not, objectively, valuable, and thus breaking out of the trance is marked with a touch of wry guilt. (A book like Drift, beloved of Bachner, is not a good candidate insofar as the breaking free is driven by an emotional need for distance and processing. A vacation book should conform to your schedule, not the other way around, and be easy to hop back into.)
But on a different kind of trip, especially my fondly remembered solitary train trips (which I won't be repeating for the foreseeable future, it seems), the ideal book is 1) immersive, 2) based on a continuous or linked narrative, and 3) amenable to contemplative reading and requiring sustained attention. This last is a subjective bit of prioritization; there are few times in my modern life other than long train rides when nothing bears on me but the desire to push on through a difficult book. A book that breaks itself into putdownable pieces unnecessarily dislodges the mind from its track while the train still chugs along its own. But absent everyday distractions, the requirement of a rapid, efficient plot can be relaxed. A slower, more meandering one is more than sufficient, as long as some momentum is maintained.
This is perhaps just to say: unputdownability is almost always desirable to both publisher and reader, but its requirements are heavily reliant on the circumstances of the reader.
* Which may include "edgy, explosive, poetic, radical, plotless work." I have no problem with elliptical and episodic and revisitation-friendly; I despise and abhor "edgy, explosive, poetic, radical, plotless work" when it comes in prose-length chunks. It is almost always self-indulgent and self-aggrandizing.
** Note also Bachner's mention of a book that was unputdownable and not of poor quality, but which she did not enjoy. Perhaps this sort of book is the most revealing, in terms of our examination of unputdownability.