Books like Merlin's Tour of the Universe
Neil deGrasse Tyson
Merlin's Tour of the Universe is 299 pages, about 5 hours 29 minutes at 250 words a minute.
6 books to read next
How long each takes
The Book of the Damned 5.8 h 
Isaac Asimov's Guide to Earth and Space 5.2 h A Fair Guide on the Revolving Sun and the Static Earth 23 min 
Ask a Science Teacher 6.4 h 
The Astro-carto-graphy Book of Maps 5.8 h 
Bad Astronomy 5.1 h Bar height shows length. Estimated at 250 words a minute.