[DreamWriter]

I just downloaded a sample of Ordinary Thunderstorms so I could see what you are talking about. Actually, those aren't hyphens. There are en dashes where there should be the longer em dashes. (If you still have the advertisement, compare the en dashes you referred to with the hyphens in "pale-faced" and "even-featured" if they show there.)

I find it very difficult to read that way too. I'm not sure why the publisher did that. It's very easy to code in em dashes. It was certainly a very poor example for Amazon to use in their Kindle advert.

I have to say that I have not seen that in a Kindle ebook before. I've usually seen the proper em dash used, two hyphens together, or space-hyphen-space.

Edited to add: When I created my husband's ebook, I did use the proper em dash. But there is a drawback, on the Kindle anyway. Kindle attempts to justify text, but it cannot hyphenate. Text is reflowable, so a publisher cannot control this either. If a line break occurs at an em dash (or an en dash), the Kindle cannot break it right after the dash, as you would see in print. Instead, it treats the word-em dash-word as a block and carries it all to the next line. This can leave a very unsightly space at the end, where the line broke. There's nothing that can be done about that. That's one reason why some people use space-hyphen-space instead of em dash in ebooks. (And others probably don't know how to create the em dash.)

This doesn't explain why the publisher used the en dash instead of the em dash in the book you cited, but I wanted to point out that there are some related difficulties with ebook formatting.