Some books which I specifically remember with fondness:
- Diver's Down: Adventure Beneath Hawaiian Seas --- available as an audiobook:
https://www.sffaudio.com/uvula-audio...by-hal-gordon/
- Little Fuzzy by H. Beam Piper --- available from
https://www.gutenberg.org/ebooks/18137 and
https://librivox.org/little-fuzzy-by-h-beam-piper/ --- be sure to also check out "Omnilingual"
http://vrici.lojban.org/~cowan/omnilingual.html and _The Cosmic Computer_
- The Mad Scientists Club books --- long out of print, they have finally been reprinted:
http://madscientistsclub.com/books.html (okay to skip the novels --- this works best in a short story format)
- Space Lash by Hal Clements --- not a children's book, but stories from the golden age which are okay for children --- I'd recommend starting at the back and working forward and bailing when things get too quaint:
https://www.goodreads.com/book/show/16036040-space-lash
- Hit the Bike Trail --- doesn't seem to be reprinted or available electronically, short, obvious story about a kid whose bike is stole and who has to ride a women's 3-speed bicycle for an overnight trip w/ a friend
- Andre Norton's _Witch World_ books --- apparently a cousin of hers lived in the rural Virginia county I grew up in, and when gifted books by her donated them to the high school library.
- Susan Cooper's _The Dark is Rising Pentalogy_ --- this book makes the world a better place when folks read it and consider the ethical issues which it raises.
Most of the others are popular enough that most folks will already be likely to have read them: J.R.R. Tolkien's _The Hobbit_, Ursula K. LeGuin's Earthsea books, Mrs. Frisby and the Rats of N.I.M.H., &c.