I contacted the Community Managers (the people who work for Stack Overflow the company) and they told me that while it technically is possible to implement this feature request, it was unlikely to happen, due to the fact that a huge portion of the Stack Exchange software relies on the tagging feature, and thus changing the tagging feature would result in all sorts of bugs.
So it doesn't look like this feature request will be happening anytime soon.
(Maybe it's time to reconsider whether we want to tag questions by the titles of books at all.)
Update: the Community Managers have asked a developer to take another look to see if the feature request is possible, based on how the code currently works. I guess we'll see what happens.