Such a view would do a lot to explain the sadness of this book, and perhaps even the sadness of ''Lonesome Dove,'' for both novels are, for all their vigor and comedy, immensely and overwhelmingly sad. But the posing of Ben Sippy as the viewpoint character serves another purpose as well, and one that may be even more important to Larry McMurtry the writer than any self-directed ironies. American popular culture has always been a rather mute one, and yet any fine writer wants to do more with words than merely master a realistic patois. That's a good trick, but if you love words, it wears thin. Through Ben Sippy, Mr. McMurtry can write of the strong, mostly silent characters of the West and yet allude to Edward Bulwer-Lytton, or speak of the wind ''keening its disquieting symphony.'' There is, finally, that hateful question, the one I have been avoiding.
Few novels are.
As vivid as Billy is, as sympathetic as Sippy is, the fascination that Sippy says he has for the gunfighter does not emerge for the reader, so that a part of the drive of the story is missing. The ending, in which outlawry dissolves to the beginning of the movies, has been done before, in the movies, and isn't effective. But it doesn't matter. When a writer is as good as Mr. McMurtry is, even a relatively minor book is a major event. Jack Butler is the assistant dean of Hendrix College in Conway, Ark., and the author of the novels ''Jujitsu for Christ'' and ''Nightshade,'' which will be published next year.