Is it a common practice to provide a chapter/section reference from the next volume in a series to the previous?

Question

When writing a series of fiction books in which characters, universe, and events are closely related, is it a common practice in English publications to provide a footnote kind of reference, for example:

A key character A meets a key character B in volume 1.

In volume 2 character A is telling C about meeting B.

I am wondering if at the end of the 2nd sentence somewhere in the volume 2 it is common practice to add a footnote along those lines:

Character A met B in Volume 1, Chapter X, Section Y.

Or is it normally left to the reader to know and remember what volume 1 read?

Answer 1

Footnotes informing a reader of which previous work an event occurred in are ubiquitous in comic books, but I've never heard of them being done in a novel before, nor would I really recommend it. The general consensus on another recent question about using footnotes in a novel was that it was a bad idea and would break a reader's immersion.

Or is it normally left to the reader to know and remember what volume 1 read?

Yes. And of course, you can't rely on that. I read the second Artemis Fowl book before I read the first one, and was relying on references to what happened in the first book in order to understand what happened in it and who everyone was. When I watched Attack on Titan years back, I managed to completely forget that a specific character existed right up until his corpse was discovered.

There's not much you can do to safeguard against this. If you spent too long explaining things that happened in the previous book(s) just in case people forgot, you're going to insult the intelligence of the readers who do remember. Just mention as much as you need to mention, then move on.

Answer 2

I don't think it's common practice at all. I also don't think it's a good idea for similar reasons as covered in Using footnotes in fiction: children's book which can be enjoyed by adults already linked by F1Krazy.

If at all possible, I'd include reminders about who this character is or when the reader might have last seen them within the text itself. In your example, the character is talking about an event (meeting another character) that the reader might remember if you give enough in-universe reminders. You can reference the place the conversation took place, the time (maybe it was shortly before the start of the war, or during that really cold winter, or during the full moon festival), or anything else that might jog the reader's memory.

In other circumstances (e.g. when the MC meets someone again they've met before) you might have the characters remember the earlier meeting, or alternatively (if that's what you're going for) struggle to remember while being unable to shake the feeling that this person seems familiar. (In that case, pointing out exactly where the character was last seen out-of-universe might even defeat the purpose.)