The Pyro already wrote about this album, so I'm not going to go into to much detail with this one. It is not my intention to undercut his review (his being a positive one), but I intend to show an alternate view (mine mostly negative). Read both and choose your own fate. (Cue evil laughter)
I've never been a big Avenged Sevenfold fan; I have their album City of Evil, mostly for that song "Bat Country" and little else, but after reading The Pyro's review (and hearing from a few others) I decided to take a gander at Nightmare...which led to a waste of my time.
Although AXS (such a stupid way to say your name) began as a hardcore/perhaps-NWOAHM band, they have completely shed that view of music (much to my relief) and have instead moved further and further into the alternative metal bracket. This album is no different, and in fact cements them into this genre (or lack thereof). Most of their songs are dull and un-inspired, blandly drifting into each other until the blessed end of the album. Not the worst album I've heard (check out my Locrian review for that one) but by far from the best. The only outstanging song is the self-titled track, which happens to be the first of the album. It contains a full thought and moves between themes and styles making it semi-(I use the following word loosely)-progressive. It is the only song I'd pick out to listen to again. A couple other decent songs were "So Far Away" and "Save Me," which is when the band slows down a bit and challenges themselves to write a song with meaning. Again it's not great, but it's better then the rest.
Well I tried to make it short, and although it's longer then I wanted, it isn't as long as I could have made it. Once again (it seems I use this excuse all the time), if you are a fan of the new-era of Avenged Sevenfold then you will probably like this album, as it moves along the same lines as before; breaking no new ground. Also if you aren't a big fan of metal you might like this album (like The Pyro), as it seems my non-metal friends who claim to 'like' metal, only do so for these alternative bands. However, if you are a huge metal-head (like myself) or you are a fan of Avenged Sevenfold's first couple of albums, then you probably should keep looking. Try the new Titan album, or the new Cough album (although the review was mostly negative, it is still some of the best doom I have heard recently), they are much better.