Okay, internet VERY unhelpful in even letting me copy the title and author, let alone the cover.
One is called One Thing or Your Mother, by Kirsten Beyer.
The only one trivial contradiction--Snyder's middle name (though it could be headcanoned as a misprint, easy enough in our world without chaos demons), and far less trivial than how the show (even before pseudo-season 8+) contradicts itself. Better yet, it links season 2 to 3 very well, which includes the Mayor (and his connection to Snyder) getting ready for "a big year coming up." It also helps promote why Spike became willing to betray Angelus to Buffy, which apparently happens almost right after (the final 2 eps of season 2).
Don't want to spoil it beyond that. I just want to say that it's more than about a child vampire. Part of me wishes they eliminated 2 eps (maybe early in the season) and inserted this book instead (which is essentially 2 stories wrapped up in one, probably need 2 ep slots to do it justice, not necessarily as a part 1 and 2).
Speaking of linking seasons, I thought this would make a good bonus ep (probably 2 parter) for linking season 5 Buffy to season 6, as in it feels like the show rather than a comic:
The Death of Buffy. As the internet is not helpful this morning, you'll have to find the other details out for yourself if you're curious.
Be sure to get it all (as it also comes in a 4 part comic), but if the cover is of the Scoobies behind Dawn putting a flower on Buffy's grave (with a ghostly image of Buffy's face, as if "in memory") then you should be able to get it. The library might be able to get it for you in this form. It intertwines the demons and events of season 5 to 6, and helps add to why they were desperate to get Buffy back (and also where Willow gets the spell from).
The only problem I can think of offhand is that there is a small scene where Dawn gets into a fight at school when another girl calls her "graveyard girl" that goes to the principal, and not something the Buffybot can handle, which would raise questions to why she's visiting her sister's grave when her sister is supposedly alive (though I like to think of it that the residents are well trained to turn a blind eye to things like that). That said, the show begs the question of Buffy's grave as well (though plenty of headcanon has come up to explain why the rest of Sunnydale and grave-prowling vampires didn't even suspect Buffy was dead), but that one scene exacerbates it.
Tales of the Slayer also strike me as good. It's an anthology (I think 4 collections, each with a theme, like one is about the 18th birthday ritual of Slayer after Slayer, which tests the Watches as much as the Slayers.) I don't think any are about Buffy, but Nikki Wood is included in one of the short stories (her 18th birthday ritual, and already pregnant with Robin). It comes in comic and text form.
And not contradict any of the seasons AND season 8+? You want the impossible. I can't help but wonder if this is a joke request.