I loved it- great writing!
I must say that this is the best piece of work I've read on this site. It's amazing and Lupin's anguish over Lily is brilliantly perfect. I have just been inspired.
The first part is great! The second part is a little confusing, but let me talk about the first part for a bit before I get into that.
I loved the Remus/Lily goodness. I wish there could have been a little more of it - it seemed like after he lost himself in thoughts of her he forgot about it. Which is okay; the whole beginning is obviously his random thoughts and musings.
I like the Marauder's Map little meme too. It's when we get to James' letter that I got a little confused . . .
The letter itself is fine, besides the fact that I'm not sure why it was written in the first place, but the whole Remus/Sirius fight just seems a little ... odd. I didn't understand who was accusing whom at first. Also, it seems a little unlike Sirius to be so quick to suspect Remus.
And the rest ... is history.
I love how you set this up. Nostalgia, confusion ... the emotions Remus is feeling are very well represented. When I clicked on this story it was marked incomplete - I think that it could work as a one-shot, but if you've got more coming that's okay too.
It's still worthy of being published on MNFF. Don't be silly. Have a nice day! *D*
I know now that you are a wonderful author.