I would be interested in your opinion of time-travel books. I've been told that this technique for exploring history has been overdone, but I still see it used.
I'm kind of tired of it. The idea, I mean. But it's not going to suddenly become unpublishable. Time travel as a mode of transit is going to be around forever.
But more to the point: don't worry about this sort of thing. Time travel, sudden deaths, giant wombats... who cares what you get your plot going with? Smart, absorbing, entertaining writing trumps all other hands. (Christ, was Criss Cross about anything? But obviously the Newbery committee didn't mind.)