A really good book devoted to dim mak is Erle Montaigue's 'Encyclopaedia of Dim Mak - the Main Meridians' and a separate follow on book called 'The Extra Meridians'.
These books cover the locations of every pressure point, the angle to strike them, the effects of striking them, how they can be used to heal, set up combinations and more.
They really are a complete encyclopaedia on the subject. If you get these two books you'll never need another book or manual to refer to.
However, I would suggest that your also receive competent instruction on this subject from a master. That's the best way to learn.