The title says it all. I'm a huge proponent of reading things that make you think, whether you agree with it all or not. I finished the book a couple weeks ago, and I'm still not sure I agree with all of it, but I have to say that Sider makes a compelling argument for taking a look at how we evangelicals view missions, evangelism and social action.
He does a good job of defining his terms to prevent any confusion over vague meanings and understandings of common "Chrstianese" buzzwords, such as "evangelism," "the Gospel," and the different parts of "social action". A small bit of his exegesis is wanting (e.g. his interpretation of "blessed are the poor", I'm not sure I agree with), but a good 95% is solid, IMHO (disclaimer: I have no formal theological training).
This is a good baseline book to read some of his other books, I think. I've read Just Generosity (dealing with poverty in the USA), but I read it before this book. I kinda wish I had read this one first.
I appreciate his thinking process, and grounding what he writes in pretty solid theological thought. perhaps if more of us Christians thought and prayed about this, and then acted in faith on it, perhaps we wouldn't be written off as hypocrites as often, or uncaring about the plight of the poor/underprivileged.