I think this book can be a good resource for congregations, although how helpful it is depends on their starting point for understanding mission.
I'll start by mentioning some aspects I think are good. The book does deal with important issues such as the changed (and still changing) context of the world in which mission is done. It speaks about issues of globalization, poverty, power, and neocolonialism. It also address the issue of "agency" and that as folks from North America, we need to focus on mission in ways that strengthen the capacity and agency of those we work with and lesson dependency on outside forces. The book also talks about culture and how culture and power in international relationships are linked. The authors use one of my favorite books, James Scott's "Domination and the Arts of Resistance," to do this which is very helpful. They write about the need for subverting power that dominates and about God's preferential option for the poor. Overall, if a congregation's starting place is a traditional view of what it means to be involved in mission (we are the center and agents of change and we work with passive recipients of our charity) then this book can be very helpful as a starting point to rethink this paradigm. Unfortunately, this seems to still be the starting point for many churches wanting to engage in international mission work.
However, I do have some fundamental problems with the book. First, it is written from a fairly evangelical point of view. The authors are Canadian Baptist and the evangelical bent definitely shows. The main Biblical text used to undergird mission is Matthew 28. In a postcolonial context, there are other passages that could better speak to how we see God's calling (Luke 4: 18-19 for example). Another important issue is that while a few sections speak to connections between our local context and that in which partners live and work, the main thrust is about how "we" work with partners in "their" context. The action takes place "over there" and North American Christians get to join with others in changing the "others" context. The authors do talk about ways to enable "participation" by all involved in mission, but just because someone participates does not mean that the issues of power have been dealt with. One of my favorite quotes comes from a book by Baaz entitled "The Paternalism of Partnership" and she writes that what is seen as partnership by one side can be seen as just another form of oppression by the other. There is another book by Cooke and Korthari entitled "Participation: The New Tyranny" which also addresses issues of changing language and practice in these relationships while not dealing with power disparities. An example of this can be seen in chapter 7 when the authors discuss Participatory Learning and Action as a formula to use when engaging with partners in "developing" areas. One of the first aspects of this engagement has to do with conducting a "needs assessment" and then, later, judging "capacities". While working in South Africa, the partner with which we worked relied on an Asset Based model which first looks at assets and capacities within a community before ever asking questions about deficiencies. When one starts with "needs" it is very difficult to ever get to the capacities of a community because the entire conversation is framed around what a community doesn't have, what it lacks, and not what is already there. In addition, while what is taught in the book is much better than simply practicing charity, it does not go nearly far enough in helping North American Christians look at their own context. Again, all the action happens somewhere else which makes it difficult for North Americans to make connections between poverty and oppression in other places and that which we experience here. Lastly, and connected to the point above, the authors constantly refer to "rich" or "wealthy" North Americans. This essentialism can serve to mask the huge disparities that exist within North America and, again, can keep us from asking hard questions about ourselves.
In sum, I do think that this book can be a starting point for engagement with churches, especially those that are more conservative. However, there would need to be much more following this, both in education and experiences offered, to help them move beyond where this book leads into a much deeper understanding of partnership and mission.