Isn't it strange that the character we are supposed to identify most with in this novel doesn't even have a name? How hard would it have been for the author to let his mom say, "Here, Jerry, meet Ursula?" or something that would let us label this poor kid? No such luck for us, though, and from start to finish our main man remains nameless.
Another thing he lacks is conventional friendship. His mom throws an elaborate seventh birthday party for him and not a single person shows up—not even the classroom booger-eater who always finds their way to parties whether anyone wants them there or not. So what does this say about poor Narrator? Is this friendlessness a choice, or is he so strange that kids instinctually avoid him? He says at one point:
I lay on the bed and lost myself in the stories. I liked that. Books were safer than other people anyway. (1.4)
But that could just be a self-defense mechanism he's put in place to avoid the angst he feels over being lonely all the time. It's kind of a who-came-first argument, though so you'll have to figure out which one is true for little Narrator. (And just to be clear, there is absolutely nothing wrong with being introverted. We are just wondering whether he really doesn't mind having any friends—even introverts have some friends.)
Either way, this is a deliberate choice the author makes. By having the narrator almost totally isolated we are able to understand why he's so willing to go along with Lettie's adventures despite how strange and otherworldly they are. If he'd been the type of kid with thirty friends, who plays rugby or cricket (it is England, here, let's not forget) and had a whole gang of trouble-makers to hang with, then when Lettie shows up with her orange sky and talk of "fleas" and "varmints" he'd be like, "See ya—gotta go play with some not-crazy people."
But instead he spends the vast majority of his time reading about ancient Egypt, or characters from the 1950s who go around solving crimes (like Nancy Drew), so maybe he is pre-conditioned to accept Lettie's oddness without much hesitation. Reading does broaden the mind, after all.
Does it strike you as just a tad odd that he seems to just accept everything that happens to him? When he sees the dead opal miner laying on his comic book, his only thought is whether he'll be allowed to retrieve it. We're pretty sure that is not what our first reaction would be (it would go something like this). Granted, he's seven, and a seven-year-old's concept of mortality is often quite limited, but we're still thinking he's pretty calm about discovering a corpse in the backseat of his family car.
Similarly, when he finds the worm-version of Ursula Monkton living in a tunnel she's carved into the sole of his foot, he just calmly tries to pull it out:
I pulled perhaps an inch of this worm—pink and gray, streaked, like something infected—out of the hole in my foot, and then felt it stop. I could feel it, inside my flesh, making itself rigid, unpullable. I was not scared by this. It was obviously just something that happened to people… (5.12)
Say what? No panic over deadly parasites, or running screaming through the hallways in sheer hysterical terror (once again, these are reactions more in line with our own). Nope—he's just all I got this, and then goes about his business like he didn't just pull most of an ancient being out of his foot and wash it down the tub drain.
He is just a calm little kid who is extremely accepting of whatever life throws at him. A friend who might be an immortal being with pseudo-magical powers? Yeah, no biggie. A creature has built a doorway into his heart and now giant hunger birds want to kill him? That's pretty scary, but nothing he can't handle. His friend's grandma (who can remember when the moon was born) can make a full moon shine on a certain part of the house just because she likes it that way? Sure, cool, no problem.
What does throw him for a loop, though, is when his father gets mad at him. For some reason he just cannot stand being yelled at by his dad—it scares him so badly that he gets paralyzed with fear. So what gives? Why is this the particular trigger that makes him finally feel fear? Honestly, we're not sure. But it does become important when he's fending off the mirages while sitting in the fairy circle and he has to face down an irate shadow-father.
Although up until this moment his father's anger has been the only thing to truly terrify him, he realizes that he has faced down worse things in the last twenty-four hours—so when his father blusters and bellows for him to come into the house (which would get him to leave the protection of the fairy circle) the boy says: "Does it make you feel big to make a little boy cry?" (12.69). Not only does this serve to make the shadow-dad give up, but also it's a turning point for the kid. Now that he's told off his dad, he can face anything the world throws at him.