Plenty of Mantra books spread across two series and a mini, with a few alternate covers. There were 24 in the first series, plus a Giant Size.
Seven books in the reboot, plus a couple of alternate covers.
Spear of Destiny was a two-part miniseries.
Here's the trick. If you're collecting these comics you are one of the few, so don't go crazy. Just be patient, look for large lots on the cheap and keep your eyes on auction sites. But if you see a gold hologram cover, grab it!
Ultraverse Flashback 