Engineer to Win by Carroll Smith. He wrote a series of "____ to Win" books dealing with race car prep. Engineer to Win has no how-to machining, but lots of explanation of design engineering such as why you should radius shafts where the diameter changes, why grade 8 bolts are not always the best, why you shouldn't use bolts in single shear, and much, much more. It has a great deal of what I covered in my mechanical engineering education & I have had a copy at hand since it came out.