Spin-0 theorem is trivial. It's equivalent saying that the complex numbers commute in products. For quite some time, I thought that locality would be required to argue spin-0 commutation, as non-commutation would immediately violate it. Of course, it's a valid argument, but can be relaxed.
I...
Siegel indeed covers many topics. But you might want to start with Chapters 2 and 3 of Maggiore's Modern Intro to QFT (unless you are a resurrection of Eugene Wigner or John von Neumann, in which case you probably won't need a textbook). It's thin, modern and proven itself over and over again...
Here's an elementary proof: http://arxiv.org/abs/1008.5382
Main points (omitting some subtleties like the massless particles and internal groups):
1) As shown by Wigner, massive spin-s one-particle states carry 2s indices of the SU(2) ("little group") fundamental representation. This is...