Looking for Canadian service records for my deceased Grandfather, served overseas.
In my position at NDHQ a few years ago, I used to go through WW2 and Korea era service records to answer Ministerial inquiries (from VAC or other MPs). As mentioned above, they're available from the National Archives for close family members at this time; eventually, they'll be more accessible to the general public once they've been deceased for a certain number of years (such as it is for WW1 vets).
For those servicemen who were in uniform only during the war, although interesting to look through, you may find that your grandfather's service records won't answer many of the questions you may have. For example, if he was a pilot in Bomber Command, it may tell you what airframes he was qualified on, but won't tell you what missions he flew, what squadron he was in or where he was based and at what times. It will give you rank info, pay info, medical and dental records, disciplinary action (if any), copies of ID photos and all the paperwork associated with being demobilized at the cessation of hostilities, but no action photos, maps, notes or after action reports. My uncle was a medic that served in Europe from D-Day to VE day but his records are very thin on what he did, where he did it and with whom. The medical records may provide some info if he was wounded of where he was at the time and what happened, and sometimes, in the case of aircrew, you may see copies of accident reports. Another of my uncles was a Pathfinder pilot for Bomber Command after having completed two tours. His records held minimum information; all the good stuff was in his personal flight log books (which he burnt a year before he passed in 1997, he didn't want us to know where he had been and what raids he had participated in, or led

).
All just to say that they're worth looking through, but it won't tell you about his regiment, ship or squadron, or what he did where, when and with whom. Obviously, if your grandfather served for a significant period after the war, then you'll find much more (and often better) info as they had more time to dedicate to record keeping.