If no-one wants to read the whole book, radgeek.com/gt/2005/01/10/andrea_dworkin/ gives a summary, part of which is below.
"If I had to try to summarize what Dworkin is saying while standing on one foot, I’d try this woefully abridged summary of her major theses:
(1) that patriarchal culture makes heterosexual intercourse the paradigm activity for all sexuality; other forms of sexuality are typically treated as “not real sex” or as mere precursors to intercourse and always discussed in terms that analogize them to it
(2) that heterosexual intercourse is typically depicted in ways that are systematically male-centric and which portray the activity as iniated by and for the man (as “penetration” of the woman by the man, rather than “engulfing” of the man by the woman, or as the man and woman “joining” together—the last is represented in the term “copulation” but that’s rarely used in ordinary speech about human men and women);
(3) that the cultural attitudes are reflective of, and reinforce, material realities such as the prevalence of violence against women and the vulnerability of many women to extreme poverty, that substantially constrain women’s choices with regard to sexuality and with regard to heterosexual intercourse in particular;
(4) that (1)-(3) constitute a serious obstacle to women’s control over their own lives and identities that is both very intimate and very difficult to escape;
(5) that intercourse as it’s actually practiced occurs in the social context of (1)-(3), and so intercourse as a real social institution and a real experience in individual women’s lives is shaped and constrained by political-cultural forces and not merely by individual choices;
(6) that, therefore, drawing the ethical lines in regards to sexuality solely on the basis of individual formal consent rather than considering the cultural and material conditions under which sexuality and formal consent occur makes it hard for liberals and some feminists writing on sexuality to see the truth of (4); that
(7) they therefore end up collaborating, either through neglect or endorsement, with the sustanence of (1)-(3), to the detriment of women’s liberation; and
(8) feminist politics require challenging both these writings and (1)-(3), that is, challenging intercourse as it is habitually practiced in our society.
But, while I hope this helps clarify a bit, you really should just read the whole book for yourself to understand what’s going on."