`eventually starting to return results about transparent space coffee pots with tartan cosies ... which is often helpful`

I don't find your examples compelling.

If you want to do an additional search that does not depend on your first terms, you simply bring up a new search window.

In your 'real world' example, the equivalent search queries would go something like

search: new crime novel

result: way way too much stuff

search: new crime novel john grisham pelican

result: exactly the right book because every one of those terms applies