Cardinal Kasper's proposal to reconsider the question of divorced and remarried Catholics and reception of the sacrament of the Eucharist has generated quite some opposition in some quarters.

For those who wish to situate the question in a broader context that is not entirely determined by internet pundits, two books by the eminent scholar John Noonan might be helpful.

1.  The Power to Dissolve: Lawyers and Marriages in the Courts of the Roman Curia—Noonan makes an extensive case for the development in church teaching on marriage's indissolubility. (Organized around actual cases, and the people behind them, it's my favorite Noonan book—it's like a beach novel with footnotes.)

2. A Church that Can and Cannot Change: The Development of Catholic Moral Teaching. The sixth section deals with marriage and divorce.