The first omnibus I ever read was a Christmas present from my wife: the More Than Complete Hitchhiker’s Guide collection—the one pictured at the bottom of the pile up there. I had read the Hitchhiker’s Guide to the Galaxy book when I was in high school, but none of the sequels.
This factoid is important because I remembered how the Hitchhiker’s ended, but the concluding chapters for The Restaurant at the End of the Universe and and Life, the Universe and Everything, for instance, were alien (haha) to me. I noted, after finishing those two books in the omnibus, that they ended unexpectedly for me. Though I sensed a conclusion to the stories in the actual narrative itself, I didn’t consider them the ending proper; lots of stories have miniature crises and resolutions pairs as the action rises to the climax. Indeed, good writers often make each chapter a sort of standalone story in themselves.
Those conclusions snuck up on me in good part because they came in the middle of the (physical) book, and not in the remaining few pages. In this, there’s a meta-narrative that helps the reader understand where he is in the story. He knows he’s near the end because there’s a lot of weight in his left hand and very little in his right.
Obviously, this phenomenon is only in relation to print books, and with assuming the reader doesn’t look at the table of contents, or forgets them. Modern tables of contents for fiction are uneventful matters. Titled chapters aren’t a common as they used to be, so there’s little to which the reader’s memory can attach.
We don’t get the same meta-narrative information from e-books, unless the percentage read vs unread is consistently visible. But even then, the reader could look at the percentage only periodically. In other cases with e-books, I’ve seen the words read/words total format at the bottom of each “page,” which isn’t terribly helpful for quick glances. If you read “28462/250192 words,” your progress isn’t so readily understood. Too many numerals, but something like “56 of 298 pages” or “60% read” is much easily grasped at a glance.
I don’t know how e-books treat omnibuses in regards to progress, but there dilemma of memory retention, by over-informing with quick glances, is still there. “76% of Book 1/5” isn’t so bad, but it’s not as persistent, in the background and via the tactile sense, reminding the reader in its own subtle way of a pending grand conclusion, as it is with print books.
Related: here’s a video of Kurt Vonnegut explaining three common story arcs, based on the protagonist’s “fortune.” I didn’t know he was pretty good at subtle presentational humor.