The End of Life: EUTHANASIA AND MORALITY by James Rachels (Oxford University: $17.95; 204 pp.) : The Right to Die: UNDERSTANDING EUTHANASIA by Derek Humphry and Ann Wickett; (Harper and Row: $18.95; 384 pp.)

Medical care has been making it harder to die. Meanwhile, the law has been trying to make death easier--at least for some patients.

In 1975, the year Karen Quinlan became comatose, no state gave legal recognition to “living wills.” Ten years later, when Quinlan died, nearly 40 states had passed such laws. They permit competent adults to set limits on medical efforts aimed at postponing death.

As the authors of two new books see it, such laws have not gone nearly far enough. What is needed now, they contend, is legal permission to hasten the death of patients when mercy and good sense demand it.

In “The Right to Die,” Derek Humphry and Ann Wickett document, at length, the struggle of terminally ill patients to have their dying made easier. The book repeats the familiar themes of the euthanasia movement: Mercy demands that active euthanasia be available to all who need it and choose it. People who help the dying to die a little faster should not be in legal jeopardy for their acts of mercy.

Humphry writes from personal experience. A former British journalist, he turned crusader after assisting his terminally ill wife in her suicide. His account of this story in “Jean’s Way” quickly became one of the mainstays of the euthanasia movement.

“The Right to Die” was co-authored with Humphry’s second wife and fellow founder of the Hemlock Society, Ann Wickett.

Their work is long on details but short on careful analysis and argument. Over one-third of the book is devoted to the history of attitudes toward euthanasia, a recital remarkable for its attention to trivia. Pages are filled, for example, with precise percentages from 1930s opinion polls.

Later chapters discuss numerous legal cases related to euthanasia. Again, the work provides an unusual test of patience. One chapter describes no fewer than 38 cases. But analysis is skimpy and scattered.

Still, “The Right to Die” could be a valuable source of information for those who are truly forbearing. Moreover, the book’s jumble of cases may be an apt illustration of American case law’s present confusion in this area.

Humphry and Wickett hope that such confusion will be reduced by legislation that is now being prepared in California. If passed, the law would permit dying patients to choose active euthanasia, so long as numerous safeguards were observed.

It is just this kind of legislation that philosopher James Rachels criticizes in “The End of Life.” The trouble, Rachels thinks, is that such laws “are so elaborate, and take so much time, that they are hardly conducive to the ‘quick and easy death’ that is the whole point of euthanasia.” Rachels’ solution: Simply let reasons of mercy count as legitimate defense against charges of homicide.

Rachels also twits most advocates of legalized euthanasia for not being completely honest, because they “almost always approve of killing in a wider range of cases” than their proposed legislation indicates. Why pretend that mercy killing should be limited to those who volunteer?

Rachels’ own defense of active euthanasia is based on a distinction between biological and biographical life. On this view, simply being alive is a biological reality that is not very important morally. But “having a life” is a biographical reality of utmost importance. It means that one has aspirations, makes decisions, establishes relationships, and so forth.

The reason that killing some humans is wrong, Rachels contends, is that it deprives them of continuing a biography. But, “where a person’s biographical life is over, or where there is no prospect of a biographical life, there is no point to insisting that biological life be preserved.” Nor is there any point in punishing those who take measures to end merely biological life.

Rachels’ reasoning leads to a number of conclusions that he does not mind calling “radical.” A husband, for instance, who kills a wife suffering from Alzheimer’s disease is not behaving immorally. Her biographical life had already been destroyed by the disease. On the other hand it is wrong to kill many animals, such as rhesus monkeys, because they do have lives in the biographical sense.

“The End of Life” contains what is so often missing in other right-to-die literature: a sustained philosophical argument for a broad agenda of mercy killing. But, even those inclined to agree with Rachels may admit that the book has an obvious shortcoming. Rachels never offers an account of the criteria for “having a life.”

Without knowing the criteria for “having a life,” we do not know whose lives, on Rachels’ terms, are morally worthy of protection. Readers of his book must piece together the criteria and then wonder about their defense. Rachels says, for example, that most mammals have biographical lives because they “have emotions and cares and social systems and the rest. . . . “

But just what is “the rest”? How are such criteria justified? And how much of “the rest” must one have in order to be certifiably worthy of protection?

Despite its surprising omissions, Rachels’ book is intriguing, and clever. Those of us who do not like it will probably find ourselves contending with it for a long time. If the significance of a book is measured, in part, by the number of minds it engages in argument, then this is likely to be an important book.