is a no no, isn't it? I know I've asked this before. If she brings up some bit of info the reader doesn't know then they will wonder what else she's witholding. If the reader knows more than the MC then that makes it exciting, doesn't it? I think that's right.
Just looking for confirmation.
Many thanks.

If the mc is your main pov character, then the reader should know the same as the mc. If the reader knows more than the mc the risk is they'll get bored while the mc plays catch-up, or they'll think the mc is thick for not picking up on the same info.
So, no, I don't think the mc has to explain it all to the reader as they go along, otherwise there would be little point in the reader reading on to discover what comes next.

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Sometimes writers try to inject suspense by setting up the MC to explain something but then they don't following through, and that's just going to annoy the reader. You can, however, have a 3rd party distract the mc, so the explanation has to wait while they are engaged in something far more interesting.

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It can be better just to keep something from the mc, rather than have the mc keep something from the reader.

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Although, saying all that, it depends on what it is. If it's backstory, then it's best to drip-feed that into the chapters, rather than start the novel with long explanations. Usually what is interesting to the reader is what happens from the point where they meet the mc, rather than the past. If there is something in the mc's past which the reader needs to know about, then maybe have it as a flashback scene, so the reader can experience it with the mc.

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Also if the mc suddenly comes out with a piece of current information which they couldn't possibly know because the reader has been with them the whole time, then that's going to need an additional scene to explain where it's come from.

I think this is quite straightforward. In terms of background, the MC always knows more than the reader. In terms of the plot, the MC shouldn't know more than the reader about something that affects the plot, or if he does, he shouldn't declare it too late in the story. A crude example is when the hero is cornered by the villain brandishing a sword, then pulls a gun out of his pocket to shoot the villain, but no one had told the reader he was packing a gun. Therefore, the gun is a deus ex machina. But if say half way through the story, the MC suddenly lets the reader know that he has a daughter, that's fine as long as it doesn't act as a deus ex machina. Which brings in the issue of foreshadowing. If you know the MC is going to need a gun at the climax, then mention it briefly early on. The reader will forget it so it acts as a surprise when it appears but a legitimate one, because you foreshadowed it (this is not a good example, but you get the drift).

For my money, there were some very poor examples of this in the last episode of Ashes to Ashes. It was pretty clear the explanation of Gene Hunt being some sort of purgatory angel had not been thought of by the writers until the near the end. Therefore, all kind of questions needed answering. For instance, why did he act the way he did if he knew all along that he was helping dead coppers to pass over to (heaven)? Which obviously is a case of the MC withholding information from the viewer that affects the plot. Solution? He'd somehow forgotten what he was. Hmmm.

Terry

The MC in my Chips, Beans and Limousines knows lots of stuff that she doesn't tell the reader, and the reader has to read between the lines to find out.

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It depends what the point of the book is. This:

"If the reader knows more than the MC then that makes it exciting, doesn't it?"

seems to imply a 'person in peril' plot - like a horror film, where you're thinking: 'Don't go in there!'

I think that's more a convention of the horror genre, leila, the reader expects certain things if the writer has taken the time to set it up.

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It's also a bit of a cliche, because if the reader knows something is coming the MC should too and prepare for it.

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- it's the difference between foreshadowing and telegraphing.

Thank you very much for this everyone - very helpful.
Yes, it was to do with plot, though terribly small in that the character reveals to another unpleasant character that she know the unpleasant character has been paid to do something rather than doing it from the kindness of the unpleasant character's heart...it might have been me being too lazy to write it in as a previous scene - but I quite liked the surprise of it though, and wondered if I could get away with it. It's not a big thing - and I can definitely see how awkward it could be if it were a big plot point. I knew there was a general rule of thumb, but couldn't remember what it was!
Thank you very much, I do appreciate it. Have a good writing day.