"Shadow Puppets" is pretty cool, but it's also included in the IDW Spike Omnibus which, unless you're hellbent on getting a hardcover, gives you a lot more (mostly great) content for your money. In particular, it has Spike: Asylum, which I highly recommend.
I've read that "re-adaptation" (they used it as filler in one of the Angel Omnibuses), and it's just a shortened version of the episode with not-that-great unmoving pictures instead of live actors. So that's worth exactly nothing.
I can't say anything about "Mystery Date" except that it seems to be extracted from the Masks anthology. Maybe consider getting that one instead?
I don't know what exactly you're looking for or what you've read already, but the After the Fall series is actually pretty good. Or, if you're a Buffy fan too, the Tales or Fray are really awesome. They also lead up to (or, in the case of some of the Tales titles, are set during) Buffy season eight. Which, granted, isn't very good. But I hear it gets better in season nine.
I appreciate the non-spoilers, because I've only read the first volume of the Boom series.
​
But man, if you want "everything," you have got quite the journey ahead of you. I've got a little free time on my hand, so here's an extremely abridged list of absolutely everything.
The Dark Horse "Classic" Series.
This is all non-canon, although I personally consider some of it to be canon.
There was a 63-issue Buffy series, a 17-issue Angel series, a few graphic novels, some mini-series, and shorts.
Buffy Vol. 1 includes what I call "Buffy: Season 0," which consists of The Origin (a more "accurate" depiction of what Whedon envisioned for the movie), as well as three stories that fill in the time between The Origin and Season 1.
Highlights: Season 0, Ring of Fire, Bad Blood, Double Cross, Haunted, Past Lives (Buffy/Angel crossover), The Death of Buffy, Note from the Underground, Angel: Long Night's Journey.
Lowlights: The Dust Waltz, pretty much the entirety of Buffy Vol. 3.
Tales of the Slayers and Tales of the Vampires
These are both canon.
There's an awesome over-sized hardcover ("Tales") which collects both of these. It's a collection of short stories about Slayers and Vampires of the past.
These can definitely be read before everything else, seeing as everything takes place before Season 1 (besides a few shorts)
Just a note: that hardcover also includes a couple Season 8 stories, and those SHOULD NOT be read until you actually get to Season 8, or you will get very very spoiled.
This is written by Joss Whedon and tells the story of Melaka Fray, Slayer of the future. It's so good, and can be read whenever, but probably before Season 8. Honestly, a good place to place this would be right where you're at, right now. There's a thread in this that ties directly into the later episodes of Buffy: Season 7.
IDW's Angel and Spike
Dark Horse gave up the rights after the shows were over, and IDW snatched them up and created a few mini-series. These were all released before Season 8 and are unequivocally not canon.
Angel Omnibus Vol. 1 (Vol. 2 is pretty worthless, although it contains a couple good stories that were released later on)
Spike Omnibus (this contains the excellent Asylum and Shadow Puppets by Brian Lynch, who will go on to some of the best Buffyverse comics)
After the success of Season 8, IDW decided to team up with Whedon (who specifically picked out Brian Lynch to write) to create the official continuation of Angel. It's very different from a "season." It's more of a quick story about what happens after the end of Angel: Season 5. This is honestly one of my favorite comic runs of all time.
Seeing as Whedon is involved, this is also officially canon.
This is a 17-issue series, collected in 4 hardcovers (as well as 4 trade paper-backs).
Spike: After The Fall also came out about the same time, is written by Lynch, and is also very good.
After The Fall was incredibly successful for IDW, so naturally, they milked the shit out of it, and like most of the Buffyverse, about 50% of this is good.
As Whedon is not involved at all, this is non-canon, although personally I include a few of these stories in my rewatches/rereads.
This includes a ridiculous amount of stuff, so I'm not gonna go into too much detail, but here's the list:
Angel (issues 18-44)
Angel: Only Human, Spike: The Devil You Know, Illyria: Haunted, and Lorne: Music of the Spheres.
Angel, issues 18-22 are entitled "Aftermath," and it is one of the worst Buffyverse stories.
Angel, issues 23-27 are all written by Brian Lynch, and are a worthwhile read
Season 9
With this season, Dark Horse got the rights to Angel back. Like Season 8, this is officially canon, as are the remaining seasons.
Buffy is really solid. Angel and Giles suck. Like, they're really really bad.
I'm tired of hyper-linking.
Season 12: The Reckoning
This is an extremely short, 4-issue, "season." Dark Horse was losing the rights to Boom Studios, but they luckily got the chance to make a quick end-cap to the entire canon.
Boom's Buffy and Angel Reboot
So Boom decided to reboot the entire universe. There's a Buffy series (which is currently on #9), an Angel series (currently on #5), and the new event 'Hellmouth' just started last week.
Boom will also release the older Dark Horse comics as "Legacy Editions" eventually.
"Shadow Puppets" is pretty cool, but it's also included in the IDW Spike Omnibus which, unless you're hellbent on getting a hardcover, gives you a lot more (mostly great) content for your money. In particular, it has Spike: Asylum, which I highly recommend.
I've read that "re-adaptation" (they used it as filler in one of the Angel Omnibuses), and it's just a shortened version of the episode with not-that-great unmoving pictures instead of live actors. So that's worth exactly nothing.
I can't say anything about "Mystery Date" except that it seems to be extracted from the Masks anthology. Maybe consider getting that one instead?
I don't know what exactly you're looking for or what you've read already, but the After the Fall series is actually pretty good. Or, if you're a Buffy fan too, the Tales or Fray are really awesome. They also lead up to (or, in the case of some of the Tales titles, are set during) Buffy season eight. Which, granted, isn't very good. But I hear it gets better in season nine.
the IDW Spike Omnibus has 1 and 3, along with a lot of either great or ok Spike stories.
http://www.amazon.com/Spike-Omnibus-Peter-David/dp/1600105394
And #15...which is very very bad, is now out in a collection:
http://www.amazon.com/Buffy-Vampire-Slayer-Spike-Place/dp/1616551097/ref=pd_sim_b_24
I appreciate the non-spoilers, because I've only read the first volume of the Boom series.
​
But man, if you want "everything," you have got quite the journey ahead of you. I've got a little free time on my hand, so here's an extremely abridged list of absolutely everything.
Thanks! The omnibus I was looking at was this one:
http://www.amazon.com/Spike-Omnibus-Peter-David/dp/1600105394
Idk why I thought it was season 8- maybe because it was right next to the season 8 Buffy collections? My bad.