Wenger's basic theory centers around the components necessary to make a community function in the work environment, especially in the "knowledge economy". He spends the first few chapters demonstrating that communities of practice (COPs from now on) are an effective way of managing knowledge, and explaining the necessity of this in today's fast-paced, ever-changing world.
He then concentrates on three main areas: domain, community and practice. Domain is making sure that the domain space of the community, the knowledge that it is responsible for, is well-defined, and not likely to be trespassed upon. This is essential to make the community self-sufficient and not trampled over by the organization. Community is strengthening the bonds, both social and professional, among the members of the community. This can happen through regular face-to-face meetings, networking in the hallways, e-mail, or ideally a mix of all these methods. Practice is the application of the domain knowledge. The COP is not very useful if its members do not continue to practice what they preach and continue to ride the cutting edge to figure out the newest applicable techniques. If the members get so caught up in the community that they are no longer active in their profession, the community will be cut off from the everyday feedback that gives it life.
The book goes on to describe some methods for developing COPs in one's own organization, some pitfalls to look out for, and finally ends up with evangelizing the wonders of the COP method. I thought that the authors have some interesting ideas that I think could be really useful in a larger organization, but in the startup companies that I am more interested in, their applicability is really limited. As noted, it's more designed for multinationals like Shell, which have hundreds of business units, and need a way to tie all of their geothermal engineers together, to use one of their examples. Still, I thought there were some interesting discussions of organizational dynamics, mostly in the context of how to create and maintain a COP, but which were generally applicable. So I think the book was worth reading for me. I wouldn't necessarily recommend it to anybody else, though.