Terisa is right, though, Meemo.
If you're 50% through Hemingway's
The Old Man and the Sea, and if you're 50% through Melville's
Moby-Dick, that's
very different, despite both dealing with the
sea.
The former is a very
short novel, and the latter a
gigantic tome.
So, it's an entirely different feeling to be 50% through a short book, and 50% through a very long one.
I always read 7 books simultaneously in a 3-day rotation. What I do to track their length, is let Marvin calculate the word count, and then I enter that word count into my Google/Readdle Calendar, next to the 7 titles of the books I'm reading, and the percentage of the book where I currently am.
That's a rather awkward, long-winded way of tracking your reading progress -- therefore I agree with Terisa it would be useful if Marvin let us display both
pages left in chapter,
and pages left in book, if the reader wishes to have those data displayed.