I came across a useful ebook the other day. It's titled Reading and Sugar, and it's by James Simmons (I think). Sorry for being vague; I've had a number of crashes this week and one crash took my sources with it. But I did find this on the IAEP mailing list. I'd really be grateful if someone could post the correct info.
I beleive this is the first draft. That doesn't matter because it's quite useful as it is.
Reading and Sugar
P.S. It's called Reading and Sugar because OLPC is the hardware; Sugar is the operating system. I only learned about the difference in the past week, and from what I can tell there is a lot more to the Sugar development community than the software on the OLPC laptop.