The Martian, by Andy Weir. This was first published chapter-by-chapter on his website and was taken down when he got picked up by a publisher. (I found this out by going to link it on an earlier thread and realizing it wasn't there anymore...)

It is serious, well-researched hard sci-fi: astronaut goes on a Mars mission, basically everything goes wrong, he has to do something with the resources available. (Opening lines: "I'm pretty much fucked. That's my considered opinion. Fucked.")