You're Aboard Spaceship Earth (Let's Read and Find Out Science Level 2)
These are favorites at our house! Mark is extremely science-oriented (and Janine seems to be following in his footsteps). He spends hours pouring over Visual Dictionaries and Wildlife Encyclopedias and watching Wonders of God's Creation and other science videos. He is really quite knowledgeable for his age. While it is no surprise that he liked these science books also, I was surprised that they were not too "simple" for him, with the availability of all those adult-level books. Much can be absorbed from these - they illustrate and explain advanced concepts at levels children can appreciate. The narrative is a blend of story and information and the illustrations (including visual aids such as colorful charts, maps and diagrams) are appealing and uncluttered. Each book introduces a science concept, then provides a step-by-step explanation within a clearly-written narrative. You may be able to find some of these at your library, but we decided that these were "keepers."