Most issues of Halls of Horror (and the various versions of that title it went under) can be found on ebay, some go for more of a price than others. Sadly there was never a compendiums or recent re-prints have ever been available (possible rights issues?).
I have most of them in one form or another - in fact as a side hobby I've been restoring some of the comic strips found in my old Halls of horror magazines and returning to them to their former glory (actually better than their former glory) by re-scanning them and giving them a nice bright sharp digital make-over at a very high resolution and they look great! Yeah geeky I know!
After completing some of my work it really is a shame they have not been collected together.
I would recomment any of the magazines featuring the strips of an artist called Brian Lewis as his compositions and action scenes are fantastic, as is his attention to detail.
The strips he worked on are:
Legend of the seven golden vampires (brilliant)
Quatermas (the first one)
Various short stories
But all the others are great too (Curse of the werewolf, Vampire Circus, Quatermas 2 etc).