Right at the beginning of this mad, maddening, provocative, and sometimes beautifully written book, “Nicole Kidman” (Alfred A. Knopf, 304 pages, $24.95), David Thomson admits that he “loves” Nicole Kidman, a confession that is both essential and superfluous. Skeptical as we all should be about long-distance psychoanalysis, Mr. Thomson’s book is more love letter than biography, both a meditation on obsession and a monument to it. He writes:

There she is in profile, her right shoulder raised, her chin lowered … with just a flap of brown cloth covering her breasts and a considerable expanse of white skin … a white that has a streak of icy blue in it, a rare milky hue. … It is the quality of flesh you find in Ireland still, and in religious paintings of the Renaissance, and it is a mysterious fusion of the spiritual and the erotic — as pale as Cranach.

To read those words is to feel a twinge of sympathy for poor Mrs. Thomson, a frisson of anxiety for pretty Nicole, and a moment of worry for President Bush — 25 years after John Hinckley, we all know that love letters to actresses can sometimes have alarming consequences. But it’s too soon to call the FBI or issue a restraining order: Mr. Thomson stresses that his love for Ms. Kidman will endure only so long as they don’t meet.

That may be just as well. When eventually they do make contact (mercifully, only by phone), Ms. Kidman comes across as “a languid, superior, but amused prefect who had called a naughty boy to her study to see what he had been up to,” an image that conjures up a mixture of repression, guilt, and vaguely masochistic peculiarity that may strike some (if not me — I am, like Mr. Thomson, British-born) as very English. It is an image that is, he supposes, deliberate: “[S]he tries to be what you want her to be.”

Mr. Thomson is simply (so to speak) projecting, but in doing so, he nicely illustrates one of his book’s wider themes. Movies are collective fantasy, their stars empty vessels into which audiences pour their dreams, longings, and delusions, a role far more demanding than any performed up on that beguiling, gorgeous screen. When Mr. Thomson claims that his love would not survive a face-to-face with his “fragrant,” “ripe,” “sexy,” “elegant,” “hot,” “glorious,” “ravishing” heroine, we almost trust him: He understands the danger of letting reality collide with fantasy, and he believes that cinema celebrity turns its creatures into people incapable of normal interaction.

If you think all this might be way, way too much of a stretch, you may have a point. Sometimes a trip to the cinema is just popcorn and 90 minutes in the dark, sometimes stardom is just a job. Regardless, don’t let that you put you off buying this book, which is a wild, berserk ride, swerving here, careering there, and narrowly missing the ditch on more occasions than I can count. But as with “The Whole Equation,” Mr. Thomson’s garrulous, insistent, and unashamedly eccentric history of Hollywood, it’s well worth hanging on until the end. Author of the wonderful, essential, and captivating “Biographical Dictionary of Film,” Mr. Thomson has a profound knowledge of the movies and a love for them that exceeds even his adoration of the goddess from Down Under. It’s impossible to read “Nicole Kidman” (how he must revel in the fact that the two of them will be linked forever, if only bibliographically) without learning far more about film, and looking at film, than the notion of a work dedicated to the life and times of a “sexy beanpole” with “commas for breasts” would suggest.

With its odd mix of biography, sharp cultural commentary, acute film criticism, and not so concealed longing, “Nicole Kidman,” as should be evident by now, is neither conventional showbiz bio, nor tabloid exposé. With the exception of one deliciously prurient detail about the filming of “Eyes Wide Shut,” gossip-hounds will be disappointed. If its writer is occasionally pretentious (he is), immodest (all those pages where he suggests how scripts could have been improved), and too prone to drool over Nicole’s “very lovely, supple body,” it only adds to this book’s ramshackle, discursive, opinionated, and besotted charm. Besides, even when spouting nonsense, Mr. Thomson is more informative and entertaining than most writers. Far removed from the arid monotony of film-school Bauhaus, the sparkling rococo of his prose is a joy to read.

Above all, don’t miss his sly, clever summaries of Ms. Kidman’s oeuvre, particularly of those shockers he believes to be unworthy of his muse’s talents, such as “Malice,” a fiasco he describes as ending up shipwrecked “on the wilder shores of denouement.” That’s a phrase so neat that I can even forgive Mr. Thomson for disclosing his dream of Nicole as Belle de Jour being toyed with by a Gestapo officer and an “elderly Chinaman.”

But can Mrs. Thomson?