I've got the Henry Gee book, it's very entertaining! I'd recommend it if you like both Tolkien and mad ponderings on science - there are chapters exploring the origins of Orcs, why Legolas can see so far and so on. I
think he's also the new editor of Mallorn, the Tolkien Society journal. If he is (don't quote me on it
) then that's promising as he writes in a lively style.
There are other "The Science Of..." books too. I've got ones on Pullman and Doctor Who.