The most persuasive description I know of what reviewing a book should entail is also, happily, the best description I know of what engaged reading is like. It comes from a 1916 essay by Virginia Woolf called "Hours in a Library," and, though the piece is longer, Woolf tames the vision in the space of about one page.

She sets up the case for the importance of reviewing by acknowledging how "oddly difficult" it is "in the case of new books to know which are the real books and what it is that they are telling us, and which are the stuffed books which will come to pieces when they have lain about for a year or two."

Readers of book reviews can be forgiven for thinking judgment comes too easily to the reviewer. Woolf pulls the curtain back -- and cripples our strut! -- by announcing that she, a better writer than any of us, finds the whole business consistently hard. A review should preserve some of that sense of struggle even as it finally settles on a judgment. And note that Woolf believes in judgment; she believes that critics should evaluate and not just give a good plot summary. We are not just separating the page-turners from the plodders. She wants us to aim for the "real," the enduring. But the measuring comes on the far side of struggle, which the reviewer represents through ambivalence.

Doing this is hard, Woolf goes on, and yet it is also our "delight to watch this turmoil, to do battle with the ideas and visions of our own time, to seize what we can use, to kill what we consider worthless, and above all to realize that we must be generous to the people who are giving shape as best they can to the ideas within them." Maybe Woolf gives us some things to watch for. Good reviews, she notes, engage in battles of judgment -- these are not publicity pieces -- and yet they are always written in an atmosphere of gratitude. What reviewer isn't desperate to be enthusiastic about a book she loves? Why read if you're not hoping for something, waiting to be gratified? Why board the book unless you want to understand something you didn't understand before or see something you haven't seen before? We don't know what that will be. We let the book issue the terms of its success, then we hold them to those terms.

A lot of books give us quick pleasures. The "real" books do what Woolf said, in a different essay about Charles Dickens: "the meaning goes on after the words are spoken." The reviewer should help us see not just the book, but also what the book is seeing. James Wood, our Virginia Woolf, talks about the task being to write "through books rather than about them." In this sense, the reviewer is like a miner: He wears a layer of the book back into daylight, where he relates what the book compelled him to see.

Lastly, Woolf goes on in that single page to do what good reviews always hope to do, which is to let the language soar to its subject -- to write like a writer and not as an auditor of a book's accounts. "Whenever there is life in them," Woolf writes, "they [the writers] will be casting their net out over some unknown abyss to snare new shapes, and we must throw our imaginations after them if we are to accept with understanding the strange gifts they bring back to us."

That image of throwing our imagination after a writer, who is midflight herself, is exactly the thing. This is "real" criticism: generous, tough-minded, hopeful for wisdom and transport. I get stuck all the time trying to review a new book -- every time. When the cold fingers of formula offer up their quick relief -- summarize the plot, quote a few bits, then say what's good and what's not, done and done -- I pull this essay off my reading table, where it always sits, within arm's reach, to call me back to the worthier task.