Thanks for pointing this out, we're on it (other formats have a similar problem).
(disclaimer: I work at Google)
Actually the epub is so badly formatted, that Google Play Books does not even process it and fails. When i run it through epubchecker/Calibre, it shows 215 errors. Probably something you want to look at.
Thank you for letting us know Lucian! I shared your comment with our publisher (O'Reilly).