Sufjan Stevens' critically-acclaimed Illinoise was one of the albums of 2005, and what we have here are 21 songs that didn't make it onto that album. We should be grateful that Illinoise didn't feature these songs - it wasn't short in its own right, and the cull that saw these songs hit the floor made it an almost perfect CD.
However, some of the songs that didn't make it are also astonishing, and those of us who would prefer more officially-available Sufjan rather than less should be grateful that tracks like Avalanche, the three versions of Chicago, and Pittsfield made it onto the shelves at some point. However, like any sketchbook, there are wrong turns - Super Computer reminds a little too harshly of the awful electronic noise Enjoy Your Rabbit album - and there are some underbaked ideas dressed up as songs.
The outtakes from Greetings From Michigan made it out onto the Internet briefly, and enhanced the understanding of that album. Avalanche does likewise, but you should only get it after you have worn out your copy of Illinoise.