I'm doing some of my own proofreading for Book 2. I've discovered something really cool that is helping me out a lot.
I downloaded an extension for Chrome that will read text aloud to me. It's got a funky robot voice, but that doesn't matter. It reads exactly what's on the page, and it makes a big difference.
One of the things I do quite often that is really irritating is typing a word twice. For instance, I might type something like, "He went went to the Lodge." If I'm just reading that on my own, my eyes will very likely glance right over the repeated word.
However, when the robot lady on Chrome reads it, I hear the mistake right away. It makes it much easier for me to find errors like that. Also, I might misspell a name like Partic instead of Patric. That's hard to see just as your reading, but it's easy to hear.
So, if you're self-editing your work, get a text reader. It's free and it really does help a great deal.