The problem is you don't really specify what area you're looking at, or your expertise/familiarity.
So two very good "intro to Canadian military" books are:
Desmond Morton, A Military History of Canada, Edmonton: Hurtig, 1985.
Allen Andrews, Brave Soldiers, Proud Regiments: Canada's Military Heritage, Vancouver, Ronsdale Press, 1997.
Both are dated, Morton's more so but it's often easier to find; if you're starting from scratch, either will point you in the right direction.