How badly is Google Books search broken, and why?

Partly this is the story that we all know: Google Books has failed to live up to its promise as the company has moved away from its original mission of organizing information for people. But the particular ways that it has actually eroded, including this one, are worth documenting, because it’s easy to think that search tools that worked perfectly well a few years ago won’t have been consciously degraded.

From Sapping Attention: How badly is Google Books search broken, and why?