After a while, no matter how well-focused, disciplined, and determined you are when writing a book, you just don't, well... see it any more. It happens to all of us at some point on every project. You spend so much time writing, cutting, revising, and polishing, that you risk either not seeing the forest for the trees or become so over-focused on one particular tree that you don't notice the forest fire until it's too late.
Okay, so I carried that metaphor just a little too far. But hopefully you've already discerned the point: there comes a time during a book-length project when you've spent so much time working on it that you lose perspective.
Here's the thing: by the time you, as a reader, pick up a copy of an author's book, the author him- or herself has read it over at least three times -- and this is after the countless hours spent writing, re-writing, and polishing. If you want to include all that, as well, then I think it's safe to say that by the time a book goes to print, its author has read it through, from beginning to end, a minimum of seven times, probably more.
This is a necessary evil. Editorial suggestions and changes must be considered and/or made, the manuscript must then be read through to make certain that these changes mesh with the overall story (tone, narrative arc, continuity, etc.), and if a problem is then discovered, it must be fixed, and the whole process starts over again.
I'm oversimplifying this because to describe the process in painstaking detail would not only rob the reading experience of some of its magic, but bore you to tears.
But when the book is finally out there, and everything looks good, the author and the editor can sit back and smile at having done their job to the best of their abilities. Authors often cite their editors as having been "instrumental" in helping to shape a book that may have encountered some rough spots along the pot-holed road to publication. Editors deserve all the credit that an author cares to cast their way, no arguments here.
But there is a group of unsung heroes in the publishing process, people whose names often don't appear anywhere in the book, but without whose effort, insight, and input, a lot of us would look like illiterate fools.
I am talking about proofreaders, those folks whose thankless job it is to go through your manuscript once you've ceased being able to see it any more and look for the signs of a possible forest fire (see over-extended metaphor at the beginning).
Many people think a proofreader's sole responsibility is to check spelling and punctuation. While that is definitely right up there on their list of duties, many of them go the extra mile -- hell, many of them go several hundred extra miles -- to ensure that the book they're working on is the best it can possibly be. The best proofreaders check for all manner of logic, continuity, plot, and character errors in manuscripts -- no machine can do what they do.
And they do this by deliberately searching out those elements that you, the writer, ceased to be able to see somewhere around Draft #3.
So consider all of the above to be a preamble to this: a song of gratitude to all proofreaders, those who labor over our manuscripts almost as long and intensely as we do, whose unblinking eye often catch the flaws that we can no longer see, and whose objectivity gives us a fresh perspective just as we need it the most.