I just began reading David Instone-Brewer's Divorce and Remarriage in the Church, and it has clarified a number of things for me already. One interesting detail is the matter of a divorce "certificate" in the Old Testament (which the Pharisees ask Jesus about). In the surrounding cultures, Instone-Brewer argues, a man could leave his wife (say, for another woman) without having to divorce her. At any time he could come back and "claim" her (and his children, perhaps because they have now become economically useful). This made prospects of another marriage very difficult for her, since any new husband would have to be prepared to lose his wife if the first husband changed his mind. (In some societies, the woman would be considered legally divorced after a five-year period of separation.) By requiring men to give their wives a certificate of divorce, the Mosaic law protected women.
What I suspect (I'm only 45 pages in) will be a key to Instone-Brewer's argument is Ex. 21.10-11: "If he takes another wife to himself, he shall not diminish her food, her clothing, or her conjugal love. And if he does not do these three things for her, she shall go out for nothing, without payment of money." While this pertains to a slave wife being mistreated when her husband takes a free wife, Instone-Brewer says this is case law, not statute law, meaning that the principle is more important than the actual circumstance (not unlike a Supreme Court ruling in the US). He writes:
Exodus 21:10-11 is case law, so we have to ignore the details about slavery and polygamy and look for the principles that apply to all marriages that involve neglect. The rabbis found the following principles in this text, and I think they were right. They reasoned that if a slave wife had the right to divorce a husband who neglected to supply food, clothing, and conjugal love, then a free wife would certainly also have this right. And they argued that if one of two wives had this right, so did an only wife. Furthermore, if a wife had these rights, then a husband was also entitled to divorce a wife who neglected him.
It must be noted that Instone-Brewer is not pro-divorce--far from it. His book deals with how to responsibly handle pastoral situations where spouses are being damaged by persistent breaking of the marriage vows. I'm looking forward to reading more.