We continue to love the Apologia elementary science books. They are very in-depth, going far beyond my own very limited science education. The experiments are fun and not too intimidating. The author of this series - Jeannie Fulbright - is herself a home schooling mother and they are written with the Charlotte Mason method in mind.
When the weather was nice, we often took the science book outside after dinner so the little boys could run around while we read. Quite often I'd soon have an additional student or two - neighborhood kids - clamoring to hear more about sea turtles or primeval reptiles. They're that good.