It seems they sometimes never even have a look at (I won't say proofread) the finished ebook before putting it on the market.
I recently bought an epub book from waterstones, it had strange random characters where accented characters should be. That was apparent even on the first few pages, so I can assume no one ever bothered to actually open the book after conversion. The accented characters where so many (it took place in Paris so there was a lot of French being spoken) that the book was completely unreadable. I put up with mistakes before (though I shouldn't have) but this time I complained (to Waterstones, not the publisher, as my relationship was with Waterstones and I believe it's their job to talk to the publisher).
Guess what, I got nothing at all useful from them (no good version of the book, no money back, and even their generic responses of how much they care were late and uninterested). At least if it was a pbook I could have returned it. I am very dissatisfied with Waterstones, and I don't think I will ever be bying from them again. You cannot read random passages out of ebooks before buying, and if they turn out to be faulty it seems that in some stores at least, there is no way of returning them.
Now, the problem about the specific book is solved, thanks to knowledgeable and helpful MR members. It was a very simple, and very stupid error of encoding. Once I removed drm and edited the first line of a bunch of xtmls, the book was as good as new (as far as accented characters are concerned - I may find other errors once I get to reading it). That's something publishers who use drm obviously don't want to allow me to do. So, they don't care enough and don't know enough to make a proper ebook, and don't want to give other people the right to correct the situation either.
That said, yes, I have seen some typos here and there in pbooks too. But they are so few and far between that they always greatly surprise me. Now I am almost conditioned to expect them in ebooks. It's insulting how they expect us to pay more money for an inferior product and say nothing about it....
(oops, sorry for the looooong post
It seems I'm angrier than I thought!)