Well the fact of the matter is that the kind of intelligence work Bond does is actually more of a combination commando/policeman than spy.
If you want to think of it in these terms, MI5 (SS) is like the police while MI6 (SIS) is like the army. One protects you from you fellow citizen and the other protects you from outside threats.
Similarly, whereas MI5, the FBI, the RCMP, etc. are concerned with lawbreakers, Bond and the SIS (and CIA, CSIS, etc) are more concerned with the elimination of potential threats.
Similar, yet different. But yes, the Bond novel certainly owes more to the detective thriller tradition at times than the Spy thriller -- it's the hero vs. the villain, as opposed to any kind of attempt at international intrigue like in Follet or le Carré.