The word appears 3 times.
The novel uses several slurs as in the first example, but the N-word shows up only 3 times. Given that these are English people in the prime of the Empire (supposedly) it is probably not unusual to expect its appearance. Also, given that most of the novel takes place in a mythical African country, its surprising that it doesn't occur more. The main character is a rather mild mannered country gent with little exposure to the world - an innocent. It is those around him who tend to be the racists.
"That's Mrs. Cohen," said Effie. "You see how it is, they're Yids."
"Oh dear," said William, "I was told to come here by the passport office."
"Sure it isn't the nigger downstairs you want?"
"Perhaps it is."
"Well why didn't you say so? He's downstairs."
(In this scene one of the reports relates how he got is assignment)
"Next day the Chief has me in and says, 'Corker, you're off to Ishmaelia.' 'Out of town job?' I ask. 'East Africa,' he says, just like that, 'pack your traps.' 'What's the story?' I asked. 'Well,' he said, 'a lot of niggers are having a war. I don't see anything in it myself, but the other agencies are sending feature men, so we've got to do something.'
Corker lit his pipe and a frightful stench filled the room. "Don't think much of this tobacco," he said. "Home grown. I bought it off a nigger on the way up. Care to try some?"
"No, thanks," said William and rose queasily from his bed.