Time frame: after when the movie took place (Origin comic) but before her parents put her in an insane asylum (Slayer, Interrupted).
Buffy goes to La Vegas to investigate this vampire factory/casino. The story is basically told by Pike, the guy Buffy hooked up in the movie and in Origins. He has to determine whether to let himself accept this lifestyle or let Buffy go. He also gets to double stake some vamps while on his motorcycle.
Meanwhile, Buffy is Watcher-less. The Watcher's Council must determine who will become Buffy's new Watcher and Giles has some competition. Even a bit of the ol' Ripper side comes out of his tweed.
Angel also shows up to watch Buffy's back and investigate the casino, although Buffy doesn't know it. He gets thrown into the 1930's through a closet portal thingy. Artistically, it's an interesting sequence since he's the only one in color in a black-and-white world.
Add a skimpy fighting outfit, time-traveling portal, vampire friendly casinoes, conjoined twins, black magic, and a priest being thrown into the water line, and you've got yourself an entertaining read.
The only weird part is that Dawn is present at Buffy's home.
Otherwise, highly recommended for any Buffy and Angel fan.