This series of books has a major problem with the experiments. I purchased the entire set to use for home schooling, and when I started doing the experiments with my son ran into a lot of problems quickly. I took the books to a local science shop and they identified that many of the experiments were missing important components. An example: one experiment in one of the books showed how to make a battery using pennies, litmus paper and lemon juice. The battery never worked. According to the local science shop it never would work without some zinc. This was information was ommitted from the book. I found using these books to be very frustrating and wouldn't recommend them to others. However, I do have friends who like them a lot. So, I guess it is just a matter of opinion.