Spanish writer snatches moments out of time; A Meditation, by Juan Benet. Translated by Gregory Rabassa. New York: Persea Books. 366 pp. $15.95.

Now the venturesome American reader can get a taste of what started a literary furor in Spain a dozen years ago when Juan Benet was honored for this dark, innovative, and elusive novel.

It is typical of ''A Meditation'' that a key passage lies buried in a quotation that is reported as something a character never did say. ''Human life is too long in the countdown of days, but very brief in that of moments. . . . Without that illusion of being able to convert time into moment - what's left?''

The novel itself seems to be attempting to bring off this illusion, converting time into moment. It does so by giving moments autonomy over time, such as a moment from the narrator's boyhood that haunts him in later life. Or any of the other moments - from a glance to an explosion - that are divided, subdivided, echoed, re-echoed, freighted with nuance, put in sequence or out of sequence, and let time take care of itself, thank you.

Herein is embedded a story of family rivalries, blighted liaisons, images of horror, episodes of farce, and some more inviting sides of life, with the Spanish Civil War as a kind of grating offstage presence. But, as the book's title suggests, the facts of the matter are less important than their reverberations.

The pretentious but earthbound musings on love, sex, and other matters are hardly worth the rigors required of the reader. Yet there is some aesthetic interest in how a book like this works. Printing it all as one paragraph looks like a gimmick. But this relentless format serves the focus on moments in a stream instead of the larger movements of time - and oddly helps pull along a persevering reader who may feel he's going down for the third time in the waves of sentences within sentences.

Why bother? For the evocation of scenes that are made the more one's own by the very labor demanded by the author. For the pleasure of seeing something in a new way. Something as simple as the narrator's view of a shattered reflection being restored to perfection in a millpond. In this he sees a parallel to the vicissitudes of a man reaching maturity and regaining a natural state of innocence and wholeness. A hopeful moment to put beside the grayer reflections of which Benet is also capable.