Do you appreciate footnotes or do they annoy you?
I took them out of my Regency romance because half a dozen people complained in the UK while others in the US said that it was interesting to pick up historical facts on the way.
One of my footnotes explained the origin of the Burlington Arcade, for example.
I find footnotes a distraction.
Well, I did remove the footnotes, so now they can't be blamed for any one star reviews. ôô
Strangely enough, the book still sells.
I think that the DiscWorld series are an excepption. As said - the footnotes are part of the illusion.
I think that footnotes would be really annoying in fiction - I have never seen them.
Andy Mcnab does put a glossary at the end of his stories (Bravo Two Zero and others). These give really brief definitions of military terms and abbreviations - for those that (in his genre) don't already know them.
I suspect that for any story with a technical element - possibly anything police/forensic for example - this could be a helpful move... Better, perhaps, than expecting the reader to do a search on the net?
Then again - as far as possible - I try to weave the "specialist knowledge" and explanation into the text. As an example - I imagine that not everyone knows what an SA80 is - so, having put on in a character's hands I will also refer to it as a rifle and I may (when appropropriate) mention its 5.56mm calibre. The trick to achieve is to get this information into the broader picture and established before I need the reader to know that the 5.56 rounds of an SA80 don't have the same "stopping power" as a 7.62 round from an SLR...
Which does, of course, mean that I have to have included something about these...
Come back frederick Forsythe - all is forgiven. (His "Day of the Jackal" includes reams of explanation) *
* I even had to explain that....
David