Is it usual to refer to the reader in a novel? The point of view is first person, and she refers to the reader at times. Can I do this?
Directly addressing the reader(s) -- both in singular and plural -- is a device that was very common in seventeenth to nineteenth century literature. It has fallen a bit out of use today, but is by no means uncommon.
Usually, if a narrator (who is not the author) addresses the reader, there is some kind of framing narrative that explains who the narrator is -- e.g. a person looking back on his life or a chance witness to the narrated events -- and who the reader is to him -- e.g. his son or a chance companion in a bar. A recent example is Patrick Rothfuss' Kingkiller Chronicles, where the first chapters relate in third person how the narrator-protagonist is visited in his exile and then tells his life to his visitor in first person -- occcasionally addressing his listener ("you").
In young adult fiction there are many examples where the first person narrator-protagonist addresses the readers without such a framing narrative, thus drawing the reader into her confidence and into the narrative.
If addressing the reader feels right to you, don't worry about it and just do it. It pushes the events clearly into the past (because if you can talk to the reader, who wasn't there, then obviously you are "now" elsewhere, too), creating a more reflective narrative style. But if that style fits you, it can work very well.
Charles Stross' Rule 34 does this, but the book is fully 2nd person. That means that you are the characters.
Some say the Internet is for porn but you know that in truth the Internet is for spam.
Rule 34 by Charles Stross
As @DanBron Said, it can be done, but it's a huge challenge to pull off.
One thing that's worth noting though is that there is a different between a 1st person that breaks the 4th Wall (addressing the audience) and a true 2nd person. If you only address the reader through the medium of the character addressing the reader, and you don't do it often, it will break the flow of the story simply because it is unexpected. To avoid this:
- use the device often,
- make it clear what you are doing,
- have a very good reason for doing it
- and make that reason clear to the reader.
The rule of writing states "Don't break the fourth wall".
That means don't remind the reader they are the reader, they read a book, the characters are in a book. Immersion is a volatile thing and worth fighting for - if the reader forgets the world around them and the book they hold in hand, but just lives and feels together with the protagonist, in the world of your story, you're succeeding - it's what puts mediocre stories apart from really good ones.
But as every rule, this one can be broken too. Break it if you want to achieve certain effects. Be it the narrator playing coy with the reader, be it humor, be it sixth sense of a character detecting the reader observing them, be it merging the worlds, the protagonists achieving a new level of consciousness and reaching across dimensions out to the reader, requesting their personal aid.
Let me quote a fragment from my most recent story, to give an example.
There's this horse - a sapient mare - right here with the protagonist (1st person narrator), inside his apartment. A bunch of thugs try to storm the apartment but circumstances (including the landlord with an Airsoft gun on a balcony above) really play against them. And including the mare standing with her back turned right towards the doorway. Two of them met her hind hooves already. Since the protagonist is in the room, without any clear view outside, most of the thug actions are reported through sounds.
Landlord's voice. “I'll keep shooting until you leave. I've got three hundred BBs in here, and another five thousand in the room.”
Another series of cracks, and several thug voices cursing in sequence. They ran around the corner of the building. [...]
Through the closed drapes I saw movement outside the window.
“Look, that's a window to his apartment.”
“Slab, did you take that molotov?”
“On a skirmish? Are you stupid? Someone hits me and I'm all soaked in gasoline.”
“Frank, go fetch the angle grinder. We'll cut the bars on the window.”
“You go yourself.”
“You've got hair. You got any clue how much these things hurt on a bald head?”
Steps running. Another burst from the AUG from above.
A moment of silence, sound of a lighter. Window opening. Cracks of BBs being launched at some six hundred FPS right onto heads of the thugs. Curses, steps running back around the corner. “Not inside!”
For a second Celestia stood only on her front hooves, as her hind legs swung in a graceful arc. A dull thud. Have you ever seen a smug horse? Imagine a smug horse. And now imagine it being twice as smug. That was Celestia at the moment.
This is the narrator being coy with the reader. It's a humorous scene where the serious enemy force met a very ragtag but surprisingly efficient resistance. The narrator is amused. The reader is amused. The mare is very amused. We can afford a small wink towards the reader, and break the fourth wall for a second, instructing them how to imagine the scene just right - just for added comical effect.
Of course you can do it. In the humorous pseudo-autobiography The Life and Opinions of Tristram Shandy, Gentleman, Lawrence Sterne even went as far as inviting certain of his readers to skip the remainder of the chapter, and then welcoming them back at the beginning of the next one. Just make sure, like he did, that it's clear who you are adressing. (He often used the reader and he for that, though occasionally he also used you or thou.)
Why would anyone go out of their way to be unoriginal in original writing? Are you sure you are writing a novel, not a school assignment?
Here is a famous example of addressing the reader (from Tristram Shandy):
I define a nose as follows—intreating only beforehand, and beseeching my readers, both male and female, of what age, complexion, and condition soever, for the love of God and their own souls, to guard against the temptations and suggestions of the devil, and suffer him by no art or wile to put any other ideas into their minds, than what I put into my definition—For by the word Nose, throughout all this long chapter of noses, and in every other part of my work, where the word Nose occurs—I declare, by that word I mean a nose, and nothing more, or less.
(The protagonist lost part of his nose in an accident that occurred while he was peeing out of the window. In the 'chapter of noses', women show particular interest in men's nose sizes.) And another one:
I am this month one whole year older than I was this time twelve-month; and having got, as you perceive, almost into the middle of my third volume (According to the preceding Editions.)—and no farther than to my first day's life—'tis demonstrative that I have three hundred and sixty-four days more life to write just now, than when I first set out; so that instead of advancing, as a common writer, in my work with what I have been doing at it—on the contrary, I am just thrown so many volumes back—was every day of my life to be as busy a day as this—And why not?—and the transactions and opinions of it to take up as much description—And for what reason should they be cut short? as at this rate I should just live 364 times faster than I should write—It must follow, an' please your worships, that the more I write, the more I shall have to write—and consequently, the more your worships read, the more your worships will have to read.
I told the Christian reader—I say Christian—hoping he is one—and if he is not, I am sorry for it—and only beg he will consider the matter with himself, and not lay the blame entirely upon this book—
Sterne also keeps making promises to readers, and occasionally even keeping them after great delay.
Obviously it's a bad idea to be as eccentric as this unless you are really good at it and want to make the eccentricity the focus of your work. But a bit of breaking the fourth wall here and there can often be beneficial in 'normal' writing.
Is it usual? No. Can you do this? Of course.
The question is not, Is there some rule against it in the Laws of Writing that All Authors Must Obey Under Pain of Death? The question is, Is it effective?
Any time you do something unusual, there is the danger that it will come across as a gimmick. If you do something unusual just to do something unusual, odds are it will sound lame. Sure, you could write a story where every sentence begins with the letter "w", and it would no doubt be challenging to write a coherent story that way. But would anyone care? Or would your efforts to make the story fit this arbitrary constraint just end up making a weaker story? But if you have a good reason for doing it, and it works in your story, than by all means do it.
Like all the other answers state, it's not a common thing to do, but there is nothing to prevent you from doing otherwise. A great example that I'd suggest you read is Italo Calvino's If on a winter's night a traveler. It's exactly what you are looking for. An entire novel whose protagonist is you.
It is not only good received by the critics and readers, but it also considered one of Calvino's masterpieces.
Another notable example is Anthony Burgess' Clockwork Orange. The narrator of the book often refers to the reader (usually when in a tough position) with phrases like 'Oh, my dear reader' and 'You are the only friend left' etc.
Yes, but relatively rare. See second person point of view:
Definition: In second person point of view, the narrator tells the story to another character using "you"; the story is being told through the addressee's point of view. Second person is the least commonly used POV in fiction, though there are a few examples. Tom Robbins's Half Asleep in Frog Pajamas is one example of a novel told in second person. Many of the stories in Lorrie Moore's book Self-Help are also written in the second person.