Some years ago I came across an online history course that was using long passages from one of my books with no attribution. I contacted my publisher who called in the company's legal team. One little letter was enough to elicit an apology and a removal of the site. All I had wanted was acknowledgment that the long quotes were mine, not the professor's. I felt bad that the course was taken down.
There's another way to handle this kind of theft. My good friend Sarah McIntyre who lives in London might have called in a bevy of lawyers when her property was stolen. Instead, her sweet revenge was to offer it free to anyone who wanted it. Sarah is an artist and illustrator of children's books and comics and does all sorts of other wonderful things that sometimes capture the headlines.