“Flights,” by the Polish writer Olga Tokarczuk (Riverhead), is exciting in the way that unclassifiable things are exciting—that is to say, at times confoundingly so. It is intermittently a work of fiction, but it is also an exercise in theory, cultural anthropology, and memoir. The narrator, an unnamed Polish writer with a hungry eye and an unappeasable need to travel, presents an omnium-gatherum, a big book full of many peculiar parts: there are mini-essays on airports, hotel lobbies, the psychology of travel, guidebooks, the atavistic pleasures of a single Polish word, the aphorisms of E. M. Cioran. Some of these riffs, which themselves tend toward the aphoristic, are as short as a couple of sentences. They are interspersed with longer fictional tales, set all over the world and in different epochs, as if they were found objects and Tokarczuk merely an itinerant gatherer: a Polish man, on a Croatian island for a holiday, searches for his wife and child, who have gone missing; a classics professor, hired as a star lecturer for a Greek cruise, falls on board the boat, and dies in Athens; a Russian mother, long tethered to the care of her severely sick son, walks out of her home and her life, and experiments with a new, perilous existence, riding the Moscow metro and spending time with the homeless; a German doctor, obsessed with body parts (he keeps photographs of vulvae in cardboard boxes), travels to a conference to speak on his paper “The Preservation of Pathology Specimens Through Silicone Plastication.”

The book’s two great themes, twining the fictional and the nonfictional ficelles, are mobility and curiosity. Like her characters, our narrator is always on the move, and is always noticing and theorizing, often brilliantly. Early in “Flights,” she tells us that she is “drawn to all things spoiled, flawed, defective, broken,” to “anything that deviates from the norm, that is too small or too big.” Later, she tells us that she loves “Moby-Dick,” a book written out of “a genuine desire to portray the world.” Tokarczuk’s approach, like Melville’s, is encyclopedic and multiform. She turns nothing away. She relishes the sites of mobility—airports, cities, hotels, trains—and all the world’s exemptions, the things that got away: “the unique, the bizarre, the freakish.” These include the living—a woman she meets at the Stockholm airport who is compiling an unfinishable book on every crime ever committed, called “Reports on Infamy”—and the dead: collections of strange specimens, such as fetuses suspended in formaldehyde, relics in St. Vitus Cathedral (“the breasts of St. Anne, totally intact, kept in a glass jar”), Chopin’s heart (an oversized organ removed after his death and preserved in alcohol), or anatomical wax figures at the Josephinum medical museum, in Vienna. Emperor Joseph II, Tokarczuk announces with apparent approval, collected “every manifestation of the aberration of the world” in his “cabinet of curiosities.”

One of the book’s most suggestive micro-essays concerns Wikipedia, which Tokarczuk rightly lauds as a “wonder of the world,” a project to gather the entire globe’s knowledge. Characteristically—because Tokarczuk is herself intellectually mobile—she changes course in the second paragraph of her riff. The problem with Wikipedia is that it can contain only what we can represent in words:

We should have some other collection of knowledge, then, to balance that one out—its inverse, its inner lining, everything we don’t know, all the things that can’t be captured in any index, can’t be handled by any search engine. For the vastness of these contents cannot be traversed from word to word. . . . Matter and anti-matter. Information and anti-information.

Tokarczuk’s book is a cabinet of curiosities that must also include itself in the cabinet, which means that, formally, “Flights” can’t really hang together, and doesn’t attempt to. It’s a work both modish and antique, apparently postmodern in emphasis but fed by the exploratory energies of the Renaissance. Its literary lineage starts in the classics (sweet-natured, knowledge-rummaging Pliny), goes through Montaigne and Sir Thomas Browne, and then winds through Rilke’s diaristic “Notebooks of Malte Laurids Brigge,” the freewheeling fictions of Kundera and the magical ones of Calvino, the diaries of Gombrowicz. This mode could be called flâneurial essayism, worldly and hospitable; its motto might be King Lear’s chastened amnesty, “None does offend, none, I say, none.” Curiosity is mobility, in this way of being in the world. Calvino’s Marco Polo enters each city and “sees someone in a square living a life or an instant that could be his.” Tramping through his fields of knowledge, Montaigne, in “Of Repentance,” describes existence as perennial movement: “All things in it are in constant motion. . . . I cannot keep my subject still. . . . I do not portray being: I portray passing.”