I'm not sure how to react to this

It seems that Lu Yan of the Åbo Akademi University in Finland teaches a Web design class and uses XHTML Essentials as a text. Trouble is, at least three of the PPT files he uses in his lectures (one, three, and four) use text from my book word for word, without credit. On the one hand I'm flattered, on the other hand I'm somewhat upset. Should I mention this to him? What do you think?