A Brief History of Time by Stephen Hawking
This book seems quite easy to understand. He talks about cosmology, and he is extremely intelligent. When did the universe begin? What was there before the universe? Will it contract? All these questions are linked to the time variable, which is considered as an attribute of the observer. Hawking is also an expert of black holes, and in this book he avoids using mathematics (although he's a master in this field). 

Isaac Newton Mathematical Principles of Natural Philosophy ;Optics
Optics: The first book records many experiments, including the separation of light passing through a prism, using maths to study rainbows, bubbles, chromatic aberrations and unanswered questions. Mathematical Principles of Natural Philosophy: he presents many geometrical demonstrations which help in describing celestial mechanics. He discusses time, space, fluid mechanics, and astronomy. He also calculates the orbit of a Halley's comet and considers irregular orbits. 

Michael Faraday Experimental Researches in Electricity


Jean Baptiste Joseph Fourier Analytical Theory of Heat


Relativity: The Special and the General Theory by Albert Einstein


Galileo: works
He uses maths and geometry to describe phenomena in the physical world. His descriptions of celestial bodies observed through the telescope are fantastic. The Discorsi sopra due scienze nuove include mathematical demonstrations and scientific understanding of structures and statics. 
