I'd love to be able to note exactly which pages I read from a book, especially when doing partial readings, and not just how many. So, for instance, being able to say I read pages 136-156 and that being counted as 20 pages read.

As a grad school student, I often read books piecemeal and need to be able to account for exactly which pages I have read.

For books I read cover to cover, this would also mean I don't have to do math every time I update my reading status. I end up having to add the number of pages from the front matter (usually a separate page count in roman numerals) to the page number I am on.