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So far I've read the first 6 chapters of the network warrior book, and must say that it is pretty good. It may be a little brief in some places if you don't at least have some basic idea of networking, but for me it covers each topic well enough, and gives you the positives and negatives of implementing certain features, as well as things that will catch you out.
I'll keep working through the book, as so far it's only covered switching, which for voice at least is a key component. There is a voice specific chapter as well, which I'm not up to yet, but looks to be interesting and informative.