When you read a book, can you tell what the author is saying to you?
In academia, people tend to be very careful about making statements about authorial intent, especially when an author has been dead for over a hundred years. So they'll talk about the narrator and what the narrator says, or they'll talk about patterns in the text that might suggest different kinds of meanings.
For current writers, the question of a relationship to the reader is a complex one as well. It's better in some ways to figure that once a book or story is published, people will get what they want out of it, on the basis of their own experiences as readers, and this may not have much to do with what you intended - especially as it comes to reading your own reviews.
But whether or not we as writers have a particular message we want to get across (as discussed here in a related post), we DO want to have control over our stories - in particular, how the information in the story gets distributed so that the story is focused and its effect is maximized in the way we intend.
There are easy and hard ways to communicate with a reader. The easiest one is to appoint yourself the narrator and say things straight to the reader. That way, if you're Beatrix Potter, you can say:
"So that is the story of the two Bad Mice, but they were not so very naughty after all, because Tom Thumb paid for everything he broke."
"And besides - I have seen that door into the back of the hill called Cat Bells - and besides I am very well acquainted with dear Mrs. Tiggy-Winkle!"
You might say that this isn't the writer speaking to us. Sure, it's not - just as I said above, it's the narrator. But the narrator appears to be using a voice like that of the author, and we might hazard a guess that the author used these devices to back us off the story, while also reassuring the reader about certain things. One thing seems clear to me in the second passage - that Beatrix Potter doesn't want entirely to leave children with the idea that Mrs. Tiggy-Winkle was only a hedgehog, but to leave them with a certain sense of wonder.
Direct narrator speaking to the reader isn't just about suddenly breaking into your narrative with discussion of "the story" and what "I" know about it. It occurs all the time in third person omniscient point of view, whenever the narrator describes something that isn't directly observable, or judgeable, by the point of view character.
And in fact, I think you could argue that there's another tool available to the writer using an omniscient narrator - since omniscient viewpoints zoom in and out, drawing closer or farther away from a particular character's judgment, the writer can choose to make these zooms, or not to, in order to control the amount and kind of information given to the reader.
Controlling the amount and kind of information given to the reader is how we keep the story under control, focused and moving forward. Keeping momentum and giving information about the progress of the main story conflict is critical. But so is providing world information so a reader doesn't get lost. That's where the problem of infodumping comes up. What is it but the problem of the writer "getting information across" to the reader? To make the story work, we have to decide what information is really critical for the reader to know.
As J. Kathleen Cheney noted in her post on description, sometimes stains on priest's hems or field-stripping of weapons appears to come into it. But why would we as authors want to give such tiny details if they're at such risk of appearing irrelevant? To keep people oriented in the world, but not only that - it's to give the impression that we as writers are knowledgeable, and more importantly, reliable and authoritative reporters of the world in which the story takes place. The description of the weapon may seem pointless because it doesn't have sufficient relevance support in story conflict, character, etc. and its only underlying message may be "trust me, the writer, because you see that I know what I'm talking about." To my mind, that message alone is not enough - yet it is a very critical one for an author to deliver, whether in sf/f or mainstream work.
Other information we give needs to keep the reader feeling like they're grounded and on their feet in the story world (whatever world it happens to be) and ready to run in whatever direction the hook pulls them, so they don't feel like they're getting dragged behind a galloping horse. I struggle with this question constantly, given that I'm trying to create the impression of very alien worlds - but at the same time I have to keep readers able to follow the complexity of what I'm doing. Typically a reader won't object to information - and a critiquer might even ask for more information - if they feel that information helps them keep oriented in a fully fleshed world. But it's a tricky borderline to walk, as you don't want people to feel you're treating them like they're stupid. I personally recommend that writers trust the reader as much as possible.
I ran across another way that an author speaks to a reader over this weekend, when I was thinking about Harry Potter (which my husband has been reading with my kids). The way you choose to name your character is very important. In my science fiction, I try to keep my choice of names grounded in a language and world system, but also to give the names a flavor that will suggest their character. Bright and dark vowels are a part of this. If you look at the wizards' names in Harry Potter, you'll realize that often, that's J.K. Rowling intentionally trying to share information with you as a reader. Take Professor Remus Lupin, for example. It would be a staggering coincidence if that were truly his last name, and further, at his birth, his parents decided to give him such a lovely wolfly name. Far more likely is that Ms. Rowling is giving him the name for flavor, and to say to her readers something like, "Nudge nudge, here's a hint and if you can figure it out I'll be proud of you."
At this point it seems logical to ask, "What if you're using strictly internal point of view?" Doesn't that make it virtually impossible to communicate directly with readers?
Well, of course not. I've discussed unreliable narrators before, and how a writer can go about separating the sensory impressions and judgments of an unreliable narrator from the total impression a reader gets. Writers can not only use tricks like inclusion of details from the setting that a character doesn't judge. We can also include details that the character does notice, but which offer something else to the reader that the character doesn't pick up on. Every time you repeat a word, or a phrase, or an association of one object with a particular type of emotion, you begin to create a pattern (often an unconscious pattern) in a reader's mind. Literary writers do this all the time, but so do writers of other genres, even without realizing it.
The other thing you can do as a writer using internal point of view is choose when to switch from one point of view to another. This will allow you to control not only what information the reader gets from which character at which time, but also to create a sense of confidentiality with the reader. The spot where a point of view switch occurs doesn't need to be at a moment of low intensity - a safe switch point. It can be at a moment of critical high intensity, a charged switch point, where it will serve the writer's intention. I love to start a situation, such as a scene when one character puts another under pressure, build up a strong sense of character 1's motives and hopefully a sense in the reader of how they want the scene to come out - and then switch points of view to the other character in the same interaction. It not only surprises the reader, it also makes them question the set of expectations they've built up for character 1 by comparing them with those for character 2. And it gives them the sense that they know more than either character does alone, creating a sense of confidentiality with the author.
Before I go, a few thoughts on pov switches. It's important when dealing with point of view switches of this type to keep your descriptions of the cross-pov phenomenon, or object, totally different. If you describe the same thing the same way from two points of view, the whole significance of the switch will be lost. This is why it's often best for a story to stick with one point of view. The difference between the two descriptions is part of the author's message for the reader. In "At Cross Purposes" (the otter story), for example, I have a facial feature for my aliens that gets described from the human point of view and from the alien point of view. My human describes the aliens like this:
"...they have no eyebrows; above each of their wide-set eyes a strip of pebbly black skin extends up to the ear."
My alien describes this same facial feature on another pair of her kind as follows:
"Both have prominent, masculine brow-character – attractive – but Kir bears a pattern like thorns, while Haa has deep folds like cooled lava."
The descriptions are different, but for me, the important part is that each description shows that the feature means something different to the individuals observing it. Because one of my favorite issues to tackle is the different ways that people understand the things that they experience, I'm excited when I get an opportunity to describe the same thing twice. Readers will notice the repetition, and that repetition will in turn bring attention to the difference between the two descriptions. And then my reader and I will be sharing something that none of my characters are experiencing at all.
It's something to think about.