Nothing fancy here. My most used is my Oxford Dictionary, but my most favorite reference book is my atlas. I love looking at maps.
Handbook of Product Design for Manufacturing, McGraw-Hill – without this book I would not have survived as a mechanical engineer, due to the fact that they taught us jack shit about manufacturing in college.
Standard for Hurricane Resistant Residential Design, SBCCI – Without this book I would not have have my own business today.
Encyclopedia Britannica Online