I own a copy of Carl Sagan's 'Demon haunted world' in my mini-library. A powerful call for science full of passionate language. But a bit dated now. Sagan's body of work was significant as was his popularizing of science.

Carl Sagan - Wikipedia

Ernst Mayr had an incredible life, and a very long one - 100 years young. His work was interrupted by the war but he got to the US and continued on with his work.

Ernst Mayr - Wikipedia

Two amazing scientists, worth knowing a bit about I think.