There are different kinds of supplements (“supplement” essentially meaning any game-specific resource book that isn’t the core rule book). In the case of Vampire, those are: Setting/scenario books; Player/Storyteller guides; Other non-setting-specific resources; “splat” books (Clans, Covenants and Roads), and tie-in fiction (clan novels, etc.).
I’ve worked on all kinds of supplements (and main rule books too). I am not a rules person, so I always tended towards the history/background/setting/story development side of things. I like figuring out the whys and wheres, hows and what-happens-next. I like providing story hooks at any possible corner. I like interesting characters who can be both a potential asset to a story, or a potential obstacle (depending on the story and how the characters deal with that NPC). I like doing the research for a setting/scenario book (I am sorry we never got to do Dark Ages: Italy).
I like the splatbooks; the VtM Revised Clanbook series was one of the best collections of clan-specific resources I’d seen in a long time; every one of them gave me ideas for a character or three I could have fun with, even with clans I normally didn’t care much about or had never played. The Libellus Sanguinus Dark Ages books (three clans per book) were also good.
Of the city/setting books, my favorites were Mexico City by Night, because all the characters described just made me smile (okay, Jaggedy Andy made me wince, too), and New York by Night. Both had a lot of very interesting, well-written characters, factions, history and neighborhood descriptions. Both had plenty of story ideas and ways for characters who are either visiting or recent immigrants (or old residents) to get involved with things going on.
But there were a few other gems:
Children of the Night contains background info and game stats for a wide range of the ‘movers and shakers’ among the Kindred, including high-ranking members of the Camarilla, the Sabbat, and the Independent clans. It’s a great resource if you want to bring in any of those widely known characters, or just reference them in passing, but it also contained some underhanded surprises.
Such as the fact that Jalan-Aajav, Seraph of the Black Hand, and Karsh, the Warlord of the Camarilla (who happened to be both Gangrel whose origins could be vaguely put at “very old, born somewhere in the Asian Steppes”) had identical game stats. Not just close or similar. IDENTICAL in every degree. Astute gamers discovered this—and MUCH online discussion ensued… Was this a editorial error? Coincidence? Were they twins? Were they the same individual, playing on both teams? As far as I know, no “official” statement was ever made public – but the speculation ran wild, and it was great fun. Because in truth, it didn’t really matter—people could interpret it any way they like, and play it as worked best for their own chronicle. (But I could imagine Justin Achilli sitting back and fiendishly enjoying himself over it all.) The rest of the book had a lot of good stuff in it too, but the Jalan-Aajav/Karsh Identity Question was just a brilliant Easter Egg for those who really paid attention (or lurked on the online forums).
I also must confess I liked the re-vamp (pun intended) and destruction of the so-called True Black Hand (aka Tal’mahe’Rah) in The Vampire Storyteller’s Guide. I’d never really liked the original concepts in Dirty Secrets of the Black Hand, because it just didn’t mesh with the rest of the VtM canon; it created this super-secret, super-powerful, cabal of super-puppet masters that took a lot of the mystery and sense of … self-determination and chaotic freedom out of the hands of player characters and storytellers when it came to how those player characters might actually have an impact on their own world of darkness. Because really, when you’re out to seize power and take over a city, or make yourself into some great powerful mover-and-shaker, it’s kind of a bummer to learn eventually that there’s already a REALLY old bunch of uptight ancients who secretly control everything, and you’re just the Wrong Clan to ever, EVER be considered as a recruit, much less someone worth taking notice of….
The crushing of the “original” Tal‘mahe’rah left behind the shattered remnants of a broken order of would-be puppet masters—their hidden fortress destroyed, their leadership killed or missing, their surviving members scattered and cut off from each other—and much better story fodder when it came to using those survivors in a ‘normal’ Vampire chronicle. (And it also made a much better foundation to tell the story of the “real” Black Hand in Caine’s Chosen, a year or two later).
(Yes, I know this is controversial, and some people LOVED Dirty Secrets, etc. Which is fine. If that’s your cup of 0+, go for it. I am MORE than happy to ignore canon when I don’t like which way it’s gone. But in this case, I think it was a necessary ret-con, and done in a way that still worked as meta-story. And yes, I stole from that revision liberally, both in work on supplements and in our own chronicle.)
By way of disclosure, the supplements I worked on:
Archons & Templars
Dark Ages: Inquisitor
Dark Ages: Inquisitor Players’ Guide
Caine’s Chosen: The Black Hand
Lair of the Hidden
Players Guide to the Low Clans
Vampire Players Guide
Dark Ages: Toreador (novel)
For Vampire: the Requiem:
The Murder of Crows (a novella contained within the anthology Three Shades of Night)