1. Although they're an acoustic duo at their core, their albums often feature other instruments such as drums, kazoos and accordions. This means even if you see them play a song live, that doesn't mean it will sound exactly like that whenever they get around to recording it.
2. They like to use a lot of morbid and hyper-sarcastic imagery. Like, almost excessively. To the point where people sometimes either miss the sarcasm and get offended, or just plain get offended. They don't do this with every song, but they do it more often than not.
3. Given their acoustic status and their association with Asian Man Records, they're often referred to as a folk punk band. I think they take it so much further than that though. If anything, Modern Americana would do it, but they experiment with traditional folk sounds, some jazzy stuff, some bluesy noises and even straight up rock songs. Especially with each new album as they add in new sounds.
Now that you are armed with this knowledge, you're ready to listen to Andrew Jackson Jihad. Knife Man continues the expansion of sounds from Can't Maintain, but I find that it in terms of lyrics the album finds a nice balance of the "finding the beauty in ugly things" from Can't Maintain and the "in-your-face anti-PCness" of Cap Guns & Candy Cigarettes and People Who Can Eat People Are the Luckiest People in the World.
In other words, this is essentially the ultimate Andrew Jackson Jihad album. I still recommend all of them, but this might be the best place for a beginner to start to get a full scope of what the band is all about.
Also, this is the best song ever:
Just listen to the lyrics and you'll understand the second
thing that I said that you should know about them.