popa_bar_abba:
Contracts Examples & Explanations by Brian A. Blum is a good, readable text. Though I am not sure they have so much on out clauses, as they are a used mostly in intricate large-scale contracts, where there are very many contingencies. Ordinary contracts are in fact very difficult to terminate without breaching. I presume that is why they instituted the “efficient breach” as a sort of legal shortcut, with a minimum of messiness.
I believe Restatement (Second) of Contracts is the preeminent directory, but I have never waded through it. Thank God I’m not in law school. 🙂