A very happy surprise, indeed.
U2 partnered with Apple to do what Radiohead did and give away an entire album for nothing except the bandwidth and the computer used to play the files. It was, as the kids say, free. But free music means you have to have an entry into the world of Apple products and an Apple ID and a device on which to store and play the files that correspond to what used to be delivered on a shiny disc. The album is a strange format nowadays, and you can tell by the cover of Songs of Innocence.
What's an "LP" and what's a factory test pressing? Who still collects these things? Audiophiles, for one, and I have a few test pressings myself, as well as radio station only releases and the like. U2 are paying homage to how things used to be--an album would come out as a test pressing when it was being introduced to the music promotion industry--hence, the scrawled text and the stamped look of this release.
What does it sound like? No idea. I downloaded it from iTunes and I'll give it the chance it deserves. You measure U2 albums by decades now, and this is the only album they've put out in this decade so it should be special and unique. Don't hold your breath for the next one--all indications are that they went through a difficult process of going back to their roots for this one, and, to me, that spells finale.