Project Hail Mary by Andy Weir

 If you liked The Martian (by the same author), you will like Hail Mary. It has that same combination of space travel, technology/physics, and humor. 

In this tome, science teacher Ryland Grace wakes up on a spaceship to find he can't remember his name or why he's on a spaceship--and discovers that the other two members of the crew are dead. Eventually he remembers (through flashbacks) that he was sent on a suicide mission to save the earth. Something is depleting the sun's energy, which will cause earth to freeze. His crew was dispatched to find a solution and send it back to earth before it's too late. What he discovers is another spaceship with an alien (whom he names Rocky) from another planet--which is facing the same problem. So the two of them decide to join forces and try to save both of their planets. They are a good team. Grace is good at the science and math, and Rocky can build or fix anything. It turns into a sweet story of unlikely friendship while they are trying to save their respective worlds. I can't wait to see the movie version of this one.