I'm new in the field and I hear these terms flying around and i'm down with most of them but when it comes to final mixing and mastering i get stunned as a person who does music and sound design so is there a difference between a final mixer and a mastering engineer and what is it (Detailed explanation and suggest reading material if possible)?
A mixer's job is to get the recorded (and edited) individual instruments and make them work together, in a way where they serve their purpose in each moment of the song.
A good book is David Gibson's
The Art of Mixing: A Visual Guide to Recording, Engineering, and Production
A mastering engineer's job is to take the final mixes as stereo tracks and polish them and making sure all the tracks sound coherent, ie there are as little differences as possible regarding loudness and frequency spectrum.
THE book is Bob Katz's
Mastering audio: the art and science.