The basics? R is our zombie narrator. He's not a gross, festering zombie with half his body parts falling off like in The Walking Dead or Resident Evil. He's still "in the early stages of decay" (1.1.2), and he's in his twenties or early thirties. As far as narrators go, he's a unique one. When was the last time you were inside the brain of a zombie? Usually it's the other way around.
Early on, R shows us that zombies can have feelings, hopes, and dreams. But everything's dialed back to a 1 (or even a .25) on the emotional scale, and he doesn't have hopes and dreams as much as he has longings and urges. Since the zombie world is dull and gray (like the flesh they have left), R longs for the vivid brightness of life.
He tries hard to be more than just Dead. His sentences are a whole five or six syllables long when most zombies just stand around and groan. "In my mind I am eloquent," (1.1.42) he tells us. It's just when these thoughts reach his tongue they get a little jumbled. And hey, don't we all feel like that sometimes?
Here's a little known fact: when a zombie eats a brain, he has access to the brain's memories. So when R eats Perry Kelvin's brain, he absorbs all of Perry's love for Julie... and falls in love with Julie himself. Being in love compels him to do things beyond riding escalators and groaning all day. Suddenly, he wants to talk about music, eat food (that isn't human flesh), smile, and laugh. Those last two are key. To R, smiling is "an unfamiliar but pleasant sensation" (1.5.53) and laughter might as well be life distilled into pure sound.
After Julie gets over her fear of R (he did eat her boyfriend after all), she starts to fall for him, too. Turns out he's pretty hot for a dead guy. This opens up a whole new avenue of activity for R: smooching. With tongue. Instead of feeding off her brain, he feeds off her passion. Like a blood transfusion, love makes R feel alive. After all, there's only one letter difference between love and live.
Even though R is Dead, he spends a lot of time thinking about being dead: dead-dead, not even a walking corpse. He imagines it full of emptiness and nothingness, and he doesn't want that. Sure, he may not have a pulse (yet), but he's got all the other stuff that makes a person alive—feelings and thoughts. So what's the difference, really?
Along with Julie, he thinks that people just kind of will themselves into death. That's why there are zombies in the first place—people got tired of really living and just gave up. Maybe that's why when he and Julie kiss for the first time, they seem to cure people of the zombie-itis. Everyone is reminded that there are reasons to keep on going. Like smooching.
So what's next? At the very end, R says "we will fight this curse and break it. […] We will cure death" (3.1.62). That makes us wonder, is death a curse? Can there possibly be a cure? And what makes R think he can decide this for everyone? But the book doesn't delve into those Big Questions. Maybe that'll be left for the sequel.R's Timeline