This is fantastic, age/stage flexible, simple and fun way to give younger and older kids an introduction to physics. There are some extension books too that include Leonardo Da Vinci Designs and Roman Machines.
I know they use this is schools but we love it for homeschooling and it has good teacher notes in the back to assist in the experiments and discussions.
We also recently discovered the Renewable DVD which is a really interesting, fun and informative DVD that gets the kids interested in the environment and how they can contribute.
We have been using these books for years and love them!!
This is a local author and an award winning series!