The book is Sanderson's "Oathbringer:"
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
It's odd that they'd use that <samp> tag, then. I can't see that it would get them anything by doing that versus just using a <span> with a class (which is exactly how they used the <samp>.
Oh, well. I'd been hoping the <samp> would somehow override the ereader's lack of monospace. Thanks for the answers.