Greg,
Odd. I'm not seeing the Google ads today. Return and
[Google Search]
give the same results. No results for sites other than
gutenberg.org.
Perhaps the Yahoo fix altered something. If someone else can replicate my original findings then perhaps add the following to the Help:
Google may include ads for other sites if one presses the return key. And no ads if one clicks the [Google Search] button.
I should have mentioned that [DuckDuckGo Search] and Return results are also restricted to the
gutenberg.org as expected.
The Yahoo search gives similar results with the Return or [Yahoo! Search]. The left side search results are restricted to
gutenberg.org. (I saw a single ad at the bottom on the first test but it was not repeatable). The right side results occasionally include a Wikipedia article related to the search but I doubt this is within your control.
If the quote is from a single book
then all three search engines return the work most related to the search at the top. If the search is, for example, a quote from Shakespeare then there is a
medley of books and there are differences in the order displayed.
I do not use an adblocker but I do use the EFF's apps "Privacy Badger" and "HTTPS Everywhere" on Firefox.
Cheers,
Rick