Hi, I came to read this out of curiosity when I saw your forum post. As a Nano novel idea, I think you're off to a great start for a story with an AU plot twist. Good luck making your word count!
On the whole, I thought this chapter was pretty well-written, and I did enjoy reading it. I think you've got an interesting story angle, although a very challenging one to write if you're going to make any attempt to keep characters in canon character. I'm already noticing that the more sympathetic Snape gets to Harry, the more out of character Snape feels to his canon character. But that's just just how AU plots usually seem to be. Characters often have to deviate to some degree from canon personality for an AU plot twist to work. Same thing with Dumbledore in this chapter. It's obvious from the start that Dumbledore is making a strange and possibly even foolish decision to send Snape to the Dursleys for Harry. I kept asking myself - if Dumbledore is so worried about Harry, and really thinks there's something seriously wrong, why doesn't Dumbledore just go to the Dursleys himself? But you obviously had to get Snape there somehow for the AU plot, so that was probably the best way you could have picked. That said, it's obvious that you ARE trying to preserve as much the character's canon personalities and speech style as possible, despite the AU plot. And I did appreciate that, because some of their canon personalities does still come through. I think you've actually done a very good job of it considering how fast you have to write for Nano, where you've got no time to worry about edits and minor details. You can always edit later if you feel changes are needed.
There are a couple of other minor points I'll just point out, if the feedback might be of any help for later on. I think you described the conditions in Harry's cupboard very well. I have to say that I'm not an angst lover, so the way this chapter started with the emphasis on how much Harry was suffering did nothing to draw me in personally, but I'm sure angst lovers will appreciate it, because it was well-written, and would make you twinge if you like angst. For my own taste, I found the cupboard description just a bit too melodramatic with how much Harry is supposed to be suffering. I think the story would actually work better and be more believable if you toned down the melodrama a bit and kept the descriptions more matter of fact, but other readers may feel differently.
The other thing I would say is that Dudley and Harry are probably around their 12-year birthday in this chapter, so for Dudley to hit Harry hard enough to cause the amount of bodily injury that's implied doesn't seem very realistic. I could believe it if they were in their mid to late teens, but not around their 12th birthdays. In canon Harry was also described as being very fast and agile, and able to outrun Dudley, so for Harry not to have easily gotten out of the way after fat clumsy Dudley hit the wall, doesn't seem realistic either. Maybe you could just have had Dudley fall on top of Harry on the stairs and squash him with his weight. But it's your story, so you may do as you please. I only offer it as food for thought.
All in all, I enjoyed this first chapter, and I'm glad I came to read it. You've got a nice writing style, and an interesting story idea. Keep up the good work! And good luck with Nano!
Author's Response: Thanks for reading & reviewing. I definitely understand what you say about characters not staying cannon and in some respects that is kind of what I was going with for Snape. I of course do not want to "ruin" him by making him some big softie or anything, but I kind of wanted to explore how different things would be if Snape had thought differently about Harry since he seemed to always think that he was a carbon copy of his father, spoiled and entitled. So I think in light of that Snape would have to change how he sees Harry. Which was also the whole point that Dumbledore was going for in sending Snape to check on Harry. He saw it as a chance to open Snape's eyes a bit more to what was really going on. (If that makes sense)
As for Dudley...I understand the ages of the boys which is why I structured the "accident" as I did. Despite Harry being agile and quick, his haste to make it to the bathroom combined with his near starved state & the confines of the enclosed space of the hallway are all factors that played into that incident. That was why Dudley was able to collect himself better and be able to get a good punch at Harry. However the point of it all (which maybe I didn't convey well enough...I'm still working on action sequences) was that it was the fall down the stairs that ultimately injured him & then the neglect of his Aunt & Uncle that was the crucial elements.
Thanks again for reading and I hope you continue to read as I update. I think the angst is done for a little bit anyways. :) At least Harry's is...mine will continue for the rest of the month as I try to reach my goal! LOL!