Books like Principles of Systematic Zoology
Ernst Mayr
Principles of Systematic Zoology is 452 pages, about 8 hours 17 minutes at 250 words a minute.
12 books to read next
How long each takes
Principles of Animal Taxonomy 4.5 h 
General Zoology 15.3 h 
History of Animals 6.0 h 
Before Adam 2.5 h 
Zoological Philosophy 7.5 h 
A General System of Nature 8.3 h 
Guide to Philippine Flora and Fauna 14 min 
Animal 11.4 h 
Fuzz 6.2 h 
Cry of the Kalahari 6.3 h 
World of Wonders 3.4 h 
Glory 7.6 h Bar height shows length. Estimated at 250 words a minute.