A couple of days ago I did a Google search for a somewhat obscure historical figure. I do it ever couple of weeks to see if anything new turns up.
Well, this one time, the top results (or near-top results) was a bundled listing of three or four digitized books about the guy. A link from that bundle led to a page of even more books. Some were fully digitized volumes; some showed just a few relevant pages; some provided only snippets.
The crazy thing is, I have not been able to repeat the search results, even using the exact same search terms. I get results, of course, but not the lovely book list. What gives?
Did you try Google Scholar ?
Might have been some differential testing being done by Google and you’ve just not been served that results format yet.
When companies have the capacity and willingness they sometimes serve up a couple different versions of pages so that they can get real world test data on how people respond to layout, organization, etc.
In case you’re not aware of it, you can probably get the book results if you do the same search in Google Book Search
Results can change, for no reasons. Maybe after Google updates their servers or index contents.
I had seen webpages simply disappear on Google results page.