Two small science books, roughly 48 years apart.
One explains the universe in simple terms, barely any math, in a few short chapters. The book is possible to read in one sitting.
The other explains advanced physics concepts, building up on a major scientific theory, with some undergrad-level equations. Just a little over 100 pages but content is very dense.
Now guess which book is, according to its own blurb, "ideal reading for the student or layman".










