The Microstructure of Matter
This was one of a number of informative booklets published by the Atomic Energy Commission back in the 1960s. This particular booklet is interesting in that it describes particle physics in accessible language just as the current standard model was coalescing in theoretical circles. A good deal of the science in this publication is unchanged, but the missing pieces of the puzzle, quarks and gluons, are not yet present. Particle physics is still a puzzle, and it is kind of neat being able to read such an artifact of its times with full benefit of hindsight.
To read this booklet. Start with the cover and enjoy a bit of the past, or just pick a page and reminisce.