How many points of view is too many?
The answer is: there is no answer. Like a lot of things with writing, it all depends on the execution. In some genres there are norms. Fantasy novels often have a host of characters, each of which get some face-time (you know, some scenes from their point of view [POV]). Think Game of Thrones. In romance, it’s common to have two POVs, the guy’s and the girl’s. In other genres, it’s a little more up in the air.
In my opinion, it’s always best to restrict the number of POV characters. When you present a new character, you’re asking the reader to learn about and identify with that character. If you ask them to do that a dozen times, you’re asking a lot. And you can lose the story in the characters. First, every time you use a new POV, you have to spend time introducing the character and setting up where they are and what they’re doing and why. That racks up the word count and slows down the story. Second, with a host of potential characters, it’s hard to have a main character. Without a main character, your reader has no one in particular to root for. (This has been my problem with GoT.) Third, the POV switching becomes a kind of crutch, I think, especially for newer writers, who often feel the need to “write into” a scene–that is, start way too soon and spend several hundred words getting comfortable with the characters, setting, and situation. Introducing a new character ends up being a convenient way of writing into a scene instead of just writing the scene. You can camouflage it as just starting a new POV, but it’s still just settling into a scene instead of starting it where it needs to start.
Finally, you’ll hear writers say that they have to have this character as a POV character. Character X is the only one who could have seen Event Y, and we have to see that event because of Reasons. But that’s assuming a couple things: that we have to learn about an event first-hand, that we have to learn it about it as it happens, and that it has to be presented as an Event (instead of as Backstory or Offstage Stuff).
If we really must learn about Event Y, then 1) have Character X show up and tell our POV character about it; 2) have your POV character learn about it through the known-on effects the Event has on the world/people around him/her (and we the reader learn about it at the same time as the POV character); 3) or allude to it but keep the details mysterious.
You only need a POV character if they have something important to add that can’t be added any other way. Ideally, they’ll have an arc of their own that ties into the larger story-arc. It’s a bit like weaving with multiple threads. Each switch has to be deliberate and part of the whole.
There are many ways to get information across, and many reasons why “necessary” information isn’t always so necessary. Don’t default to adding a new POV just because it’s convenient.
All that being said, multiple POVs can work. Sometimes, the best option IS to add another POV, or many POVs. The aim may be a more intricate, varied plot. Sometimes, there really is no other way to get across a certain bit of plot.
Let me give some more concrete examples here from my own writing. Channing has two POVs: Everett’s and Caroline’s. We start with Caroline’s, then switch back and forth for a while. Then we stay with Caroline, then begin switching back-and-forth. We start with her so that we can meet Everett and his cousin Harry through her eyes and so that we don’t know certain things about Everett and Harry until later (for example, we don’t learn until later that Harry and Everett are cousins). Later, we stay with Caroline because I want readers to be surprised when Everett pops back up. Then, when everything starts heating up, we jump back and forth as their interactions become more intertwined. Everett and Caroline each have their arcs: Everett learns to be happy in the moment instead of giving up everything for his antislavery crusade, and Caroline grows up and figures out her feelings about slavery and life in general. But this is all part of an overall arc: girl meets boy, girl and boy are pulled apart, boy and girl come back together.
[Full disclaimer: I added four chapters, two each from the POV of Harry and Augustine, not to get across information per se but because I wanted to write from their perspectives. It gives a little more insight into them as characters.]
Another example: I wrote a prequel to Channing about the characters’ parents. So, from the beginning, it was natural to me that there were four POVs, as it was two couples (three if you count the brothers as a “couple”) who come together and then fall apart. I leaned heavily on Archie, since he was a common thread between the other three characters–lover, brother, and master. The overall arc is fairly simple: brothers start a feud, brothers try to destroy each other, one of them succeeds (actually, they both succeed in a way). Each of the four characters has an arc of his/her own: Archie loses his faith in his brother and loses everything, Emily’s dreams are crushed but she dusts herself off, Charles ruthlessly attacks his brother but realizes too late that there’s no joy in it, and Betty goes from naivety to taking charge of her destiny.
Of course, choosing who will act as POV character and when can be tricky. Don’t think that the above all came naturally. Especially with Channing, it took a lot of trial and error before I figured out how to approach the story. But taking the time to work it out was worth the effort.