Read this years ago when I was a kid and really liked it. Even though it was published in 1979 and a lot of the info is out of date, this is still a fun book with interesting facts and great pictures.
It's really only a two-star book at best; over-general and simplistic, even for its intended age range. However, I haven't seen this book since the first grade, and it brought back a rush of pure golden nostalgia for my geeky awakening as a child...so it gets a ratings boost for the memories.
This is a 5 star book not because of the content but because the approach this book which has yet to really be repeated. They attempted to take real science and communicate with the help of the Star Wars universe. If science could be taught this way more often, the world would be significantly more science literate than the current situation where the science culture and pop culture have significantly diverged since the time of the writing.