Just searched for the Books Etc. website and the results page contained an inline ad for Waterstones, one of Books Etc. biggest competitors:
I’m not sure whether Google’s trying to be helpful by displaying results from similar searches, or if this is a paid-for service. If the latter, I don’t like it very much. Admittedly it’s clearly separate from the other results, but it’s not relevant to my search! I’d far prefer it to be over on the right hand side, like ads have been previously.