Annie Dillard is a creative writer-turned-literary critic. Her first book, ''Pilgrim at Tinker Creek,'' was the book of a lover of nature, reveling in the turning of the seasons in the Blue Ridge Mountains, a journal of self-discovery. Her second, a book of poems called ''Tickets for a Prayer Wheel,'' featured her love of natural things, ancient sycamores, starlings, muskrats, mantises, cicadas, and frogs.
Now, perhaps on the principle that Kipling advocated to a writer, ''When you can do something well, do something else,'' the pilgrim at Tinker Creek has become a pilgrim of fiction. ''Living by Fiction'' is a set of loosely connected essays, dealing with modern fiction all the way from James Joyce and Gertrude Stein up to and including John Barth and Jorge Luis Borges.
Her book is mostly a series of unanswered questions, suggestions for further thought. She has read, for example, the avant-garde ''Invisible Cities,'' by Italo Calvino, a book in which Marco Polo reports to Kublai Khan on the many cities he has found in the khan's realm:
There is the city hung from high nets suspended over a plain; there is the city whose inhabitants stretch string all over town to delineate their every relationship, until the strings make a web in which no one can move; there is the city whose carnival stays put year after year while its banks, docks, and municipal buildings are loaded on trucks and taken on tour.
After reading from books like these, Dillard asks us, ''What, in the realm of imagination, could be the difference between invention and discovery? And is not all the world the realm of Kublai Khan, the realm of the imagination?''
As a naturalist in the house of modern fiction, Dillard loves to lose herself in speculative thought. Are the great novels of our time being lost to our view because no one is paying attention? If such a great novel came along and its editors directed it toward the mass market - by mistake, of course - ''Would a lover of literature pick up a novel aimed at the readers of 'Airport'? . . . I hope that a future army of graduate students will pore over ignored novels and rescue the literature, as 'Moby Dick' was rescued.''
In short, Annie Dillard wonders: Is anyone minding the store? If someone wrote the Great American Novel today, would we find it in time? Or, at her most mystical and, as she admits herself, fantastic: Is man-the-maker holding the world together? Is it possible that ''the universe needs somebody or something to keep it from falling apart?'' ''A completed novel in a trunk in the attic is an order added to the sum of the universe's order. . . . Could a complex and ordered novel pull the stars from their courses?''
The reader can see that Dillard places a high responsibility upon the artist. Though at times she realizes that she is asking too much, she nevertheless holds firmly to the thought that art interprets life, makes it meaningful, creates life's meaning as truly and as fully as does philosophy.
This is a book full of wonders. Annie Dillard moves among modern writers and artists like a small child picking up pebbles on the beach, examining each with curiosity and delight. She is never dogmatic, always open-minded. The bad news is that she rarely analyzes the grounds of her admiration. The good news may be that she is contemplating writing a novel of her own.