I have really enjoyed Terry Pratchett's books ever since my brother introduced them to me several years ago. They have so many wonderful layers - you may just skim the surface and read with exquisite enjoyment or you can read a little more slowly and discover the layers beneath connected to Mr. Pratchett's many areas of expertise.
One of the central characters in this children's book is Mrs. Tachyon who has a cat called Guilty "with his fur like carpet underlay, broken teeth and boomerang-shaped backbone" and a shopping trolley filled with strangely moving black plastic bags. She is seen as a "bit.... touched", but it transpires that she lives and moves between many "time trouser-legs". If you look up the meaning of her name you find that tacho is derived from the Greek for "speed, swift, fast" and that a tachyon is any hypothetical particle that travels faster than light!