Daniel Johnston’s long battle with mental illness is no secret — but as proven by the loyal cult following he’s had for years, neither is the one-of-a-kind genius of his outsider art. In addition to the high dollars his idiosyncratic drawings fetch on the art market, Johnston’s songs have been covered by scores of hip artists such as the Eels, Conor Oberst, TV on the Radio and Tom Waits. Johnston’s funky way with tempo and his high-pitched, pinched vocals were never exactly manna for the mainstream, but to those who get past the surface roadblocks, his music is sweetly melodic on a Beatlesesque scale. The West Virginia-raised and Austin-popularized Houston resident sings about love like a child who has been given a taste of it but only yearned for it since. In Johnston’s world, things are fairly simple: good is good, evil is evil, love is good and whatever opposes love is … evil. The 2007 collection The Late Great Daniel Johnston: Discovered Covered offered two discs of such gems, one featuring covers by some of his most famous fans and the other featuring the same beautifully basic missives sung by Johnston himself with utterly charming, unguarded abandon.