There has been a lot of science related stuff going on here lately. I borrowed a science book recently. It was a science book meant for younger kids called Mada or science, in hebrew. It turned out to be a translation of a book called Why Why Why Do Magnets Push and Pull , I can't speak for the original but the version I read was very well done. Simple text which still managed to pack a lot of information into small space, nice illustrations, nice selection of topics and most importantly conveys the point that one can find science all around us, on playgrounds, cityscapes, etc. I think it's a nice book to use as a springboard for further discussions and explorations. The same day I also borrowed a few textbooks, just to check out scope. One was an elementary textbook for nature study and the other an elementary text for human anatomy and physiology. I was very favorably impressed with both. It was the first time I've seen an Israeli frum textbook. I really enjoyed looking through them. I think they could be quite useful to use as spines for science and I was really delighted to see a science text that includes related verses from Tanach, the local geography, flora and fauna, etc. I think the Jewish community in the Diaspora would be well served if someone would translate something like this into English, maybe someone already did, I just don't know.
I've been doing some science tricks (experiments really) for the kids and they've been enthralled and asked for repeat performances. In the past this hasn't worked as well, but now it seems the time is right and everyone from young to old is very excited about it. I also think it creates very positive associations for the kids when they think about science and might be interested to explore further. I just wanted to mention a few more resources that we've found useful in our scientific adventures.
Back to Basics - even though this is not technically a science book, there are many many areas discussed in it that have to do with science - gardening, animal husbandry, dying, environmental considerations, building, engineering, etc. One of my kids loves to look at it and talk about different things inside.
Different "how things work" books are obvious good choices for learning about science. There are many great popular science books that would be great for older children and up. Field guides to birds, plants, etc and other well illustrated reference books.
Let's Read and Find Out series for children are very informative and well done, at least the few I've seen this far.
Real Science 4 Kids - we have only one of these so far, but my scientifically inclined son liked this and my scientifically inclined husband said it was sound and well done from the scientific point of view:)
The Animal Atlas -another family favorite, beautiful animal pictures with some additional info and geography, I might very well have to get another one of these, the old one is coming apart.
We also have enjoyed reading different children's books touching on various subjects relating to science indirectly and generally often discuss subjects of interest that have to do with science as they come up. So far this indirect approach has worked for us but as kids get bigger we might move into more "official" science, time will tell.