I have in front of me the proof copy of Unmortal, which I have spent part of a day reading and annotating. At this rate I'll need about two weeks to go through the whole thing (although money's on me getting through it a lot faster than that; I'm just an underpromise-and-overdeliver kind of guy). Once again, the experience of editing this book has confirmed for me how important it is to come to each successive draft of a work with as much distance as possible as you can manage. The more you can make it feel like someone else's work, the better.
Editing one of my books tends to go like so: once I've completed all the major rewriting, to the point where I can't discern any more structural changes to be made in the story, I make a copy of the book (this I do for each draft anyway) and change the base typeface. (If you edit in a serif font, use sans-serif, or vice versa.) I picked up this trick some time ago and it's stood me in good stead ever since. Your eye is forced to actually read the thing instead of just skate over what some part of you recognizes all too well.
I'm also convinced the modality of the editing matters. Way back once upon a time, when dinosaurs roamed the earth and programmers used toggle switches on the front panel, I'd print out a manuscript in double-spaced font, put it into an L-ring binder, and edit that way. Eventually screens got large and comfortable enough for me to edit on directly, and I hated the sheer cumbersomeness of paper edits to begin with, so that technique fell out of fashion for me.
When I started self-publishing and getting in proof copies, the old habit of marking them up by hand came back real fast. One's editing instincts seem to flower differently when something physical is in your hands, and it was far easier to have those instincts come forth when you had something that actually fit in your hands instead of requiring most of a tabletop. Eventually, each book I released enjoyed an edit pass in that form.
I've been surprised, pleasantly so, by the way the rise of ebooks only seems to have further stimulated the sales of physical books. I suspect it's because the two formats serve different ends. If I want something to just read, I'll opt for the digital version; if it's something where I want to own it, I go paper. The recent re-release of Letters To A Young Poet (with the other half of the correspondence restored) was something I knew I wanted as a physical artifact. But something like Cliff Simak's back catalog, all material I want to get caught up with first before figuring out if I want to adorn my shelf with any of it, I'll pick up digitally, if only because there is so dang much of it.
One has a different relationship with a distinct physical artifact than with a bunch of bits — yes, even when that artifact exists in many hundreds of thousands of copies. And especially when it only exists as a single proof, marked up with your own two hands.