Nowadays, it seems there is increasing pressure on self-published authors to ensure that their books are not just good but perfect in every way. In a large part this is because of the undeniable fact that some self-published books are not of a professional standard and that reflects on the rest of us, however good we are. This has led to an expectation amongst many readers that all independently published books will have errors, which are pounced on, sometimes gleefully, as proof that the self-publisher cannot be 'professional.' The unfortunate author ends up feeling insecure and full of self-doubt when the truth is that there are no more errors in their books than appear in traditionally published books, and quite often a lot less.
As well as writing, I work as a line editor, copy editor, teacher and reviewer, all of which require an eagle eye for typos, grammatical errors and plot and characterisation discrepancies. Almost every traditionally published books that I have read in the past year had at least one typo, usually a lot more. The truth is that the odd typo doesn't matter. Allowing a brief moment of disorientation to spoil my pleasure in an otherwise good book would be ridiculous. Unless I'm being asked to edit the book, I briefly register the error and move on. Of course too many typos become annoying and impinge on enjoyment of the book, but, unless the typos are very frequent or serious enough to impact on understanding the story, the best thing is to forgive and forget.
Of course, editors do more than just check for typos, and I am more likely to object to the sort of things that destroy my belief in the story. This includes characters that act in an unbelievable way without good explanation, and plot coincidences that are totally absurd. I'm also irritated by books set in historical settings in Britain where the characters come out with American terms. Recently, the word 'gotten' on the lips of a Victorian, middle-class, English lady jerked me right out of the story. That said, it was a well written, amusing book and I enjoyed it.
So, back to the beginning. Nobody's perfect and nor are most of the books that are published. That doesn't mean that we writers shouldn't strive for perfection, good editing is essential, but it's equally important not to beat ourselves up when, after publication, a helpful voice says, 'By the way, I thought you'd like to know, on page 200 you should have had a comma...'