The Risky Art of the Multi-Character Point of View
Literature has a long history of novels with different characters offering their own points of view. In the English language alone, you have example that range from classics such as Faulkner's As I Lay Dying to works by modern authors such as Nick Hornby and Tom Perrotta. It's a technique that lends itself to a variety of styles and devices, from expanding a story across distance to introducing unreliable characters to build intrigue.
Also, agents and editors hate it.
There are many reasons why multi-POV stories are a tough sell, but I have a few hypotheses. The big one is that the technique has been so badly misused and overused in recent years that no one trusts it anymore. A lot of self-published authors and serial writers use multi-POVs as a sort of preemptive defense against head-hopping - something they still do, but it's okay because those heads are clearly labeled.
Mind you, that's hardly the only way to ruin a story with multiple POVs. I've seen mystery writers use multi-POV to completely spoil the mystery. I've seen authors whip back and forth between characters so quickly that I had to take a break to relieve the nausea. Nevertheless, the constant favorite seems to be one POV for 95% of the book, with peripheral POVs used to cheat and reveal things that this character couldn't know.
I have a bit of experience with multi-POV novels. Allow me to share.
Competing Unreliable Narrators
The novel: Nerd World
The gist: Four teenagers involved in an academic event that gets a little cutthroat. This started life with one POV - panic-prone whiz kid Apollo "Paul" Liston - but the story grew out from there once I realized how much of the story was only seen by "off-camera" characters and how much of the central story was open to interpretation. Thus, it received three additional interpretations - the manically geeky Ken Greevey, blase outsider Jane Anders and malignantly obsessed Aaron Bellamy.
This kind of perspective shifting is tricky. The characters need to sound different and they need to have enough to do to justify keeping them around. To solve these problems, I created a schedule for each character so that I'd know where they all were at any particular point in time and assembled a little style guide for their monologues. I don't necessarily recommend this much prep and wouldn't do it today, but it helped at the time.
The result: Nerd World has appeared in a few different venues over the years and I've never received any complaints about the POV shifting. If anything, it's a selling point - people like the characters and like even more that they get to see them in their natural habitats.
On the other hand, the one remark I received from an agent was negative - he insisted that the POVs were pointless and confusing because they all "told the same story." Now, I could absolutely rewrite Nerd World as Paul's story alone, but I'll defend the competing POVs to the death. Taking them out would cost too much. You'd lose a significant female perspective (in a type of story where that's rare), the chief villain would go from a "hero of his own story" type (you know, the kind agents swear they want to see) to a dude who hates the protagonist for no reason, a lot of little subplots would no longer be viable, and the overall structure would just become kind of bland.
In any case, it looks like competing POVs are out - but what about a story where the characters really are telling completely different stories?
The novel: The Fabulist
The gist: Alternating chapters containing two linked stories that take place on either side of a global catastrophe. The odd chapters follow a nameless protagonist on a quest across a scorched wasteland, while the even chapters follow a big galoot on his last few days of life before the activation of a doomsday device. Once upon a time, these were separate novels with related characters, but a significant round of rewrites united the two into a grander narrative.
This was always a gamble. The link between the two narratives doesn't become clear until about a third of the way into a relatively long novel, and then it's completely turned on its head in the last few chapters. For the first few chapters, one might be forgiven for seeing two distinct stories, a serious risk with this structure. Another potential pitfall is that one of the narrative ends up being a lot more interesting than the other and unbalances the whole thing.
The result: I'm not sure that I've ever heard anyone comment on the dueling narratives, positively or negatively. That's a real surprise. Stories that lurch back and forth in time have become something of a cliche in recent years, and the more common a device is, the harder it becomes to sell.
The closest thing I received to a comment on the narrative structure was from an agent who praised both protagonists, said that she was really in seeing what would happen to them next, clearly viewed both sides as equally strong...and then passed anyway without giving a reason. That's something you'd better get used to.