When I read on my Kindle, I highlight errors as I find them. If it's a self-published book, I send the clippings file to the author once I've finished it. Most authors respond positively, and fix the mistakes (and in at least some cases, find others and fix those, too).
I'm less sure what to do when the book has been published by a traditional publisher. The one time I tried to contact a publisher (to tell them that I wanted a book, but wasn't prepared to pay more for the Kindle edition than the paper edition), I found it really difficult to find the right e-mail address to use.
I recently finished Empire of Ivory by Naomi Novik, and found that it has some really bad mistakes. I'm guessing that they're due to the
publisher giving less love to e-book versions, but whatever the reason, I'm really unimpressed, and I'd like to let the author and/or publisher know. So far, I've only really tried to contact the author, since if the mistakes are due to e-books getting less attention, she's probably not aware of the issue, and I'm assuming she will care more than the publisher.
So, how do I contact the author and/or publisher? What's the best way to find contact details for them? The best option I could find for the author was Twitter. I tried tweeting her, but haven't received a response.