I am searching for a book that I first read back in elementary school, in the 1970s. The book was illustrated, and around 100 pages.
It concerned astronauts in a war with these aliens that were skeletons, or bone men if I remember correctly. The bone men had uniforms, but didn't need air to live on the moon, and the astronauts were able to fight them using magnetism, and could fire at them with ball bearings or hammers.
I'm sure it was a part of a series of books that were science fiction for kids, and as I read these back in the 70's, maybe published in the 50's or 60's.