We got a new book about Wikipedia  recently, and it prompts us to devote some space to this remarkable Web creation.

In case you missed the opening credits, Wikipedia is an online encyclopedia with 9 million entries, tens of thousands of unpaid contributors and editors, and you can read it in any of 250 languages. By the way: It's all free.

Unlike a traditional encyclopedia in book form, Wikipedia exists only on the Internet. Also unlike a traditional encyclopedia, it is updated continuously. Encyclopedias such as Britannica or World Book are usually updated annually or semi-annually. If you have the book version, a new volume comes out to add whatever significant changes have occurred, usually in history and the sciences. But Wikipedia is updated daily, even hourly.

How will the encyclopedia companies survive? In straitened circumstances, no doubt. The Britannica is also online now, and can be read there for a subscription fee of $70, renewed each year. It also includes access to articles from 403 magazines, which is nice. There's still a print version, which sells for $1,400.

We don't know how long it took Britannica to face reality, but we know when the moment began. We've been doing this column long enough to have been pitched on the first CD version of the Britannica, for which the company wanted $1,000, almost exactly the same price as the bound volumes. There's no way on Earth you're going to be able to sell this for a thousand dollars, we said. Why not, the company said, it's the same information. And so, as the poet sayeth, the long night began.

Unlike the traditional encyclopedias, anyone can write an article or make an addition to Wikipedia. But it's a good idea to start by playing in the sandbox. Just go to the Wikipedia Web site (Wikipedia.org) and type "WP:sand" in the search box. Then make any changes you want. Or plunge right in. Joy recently did this and added some information about Bertha Palmer, the imperious wife of Potter Palmer, a railroad car tycoon of the late 19th century.

What about false information? How can Wikipedia prevent scurrilous entries? Well, in the same way any publication has to handle its material: by editors going over it. Wikipedia has tens of thousands of editors, nearly all volunteers, a mix of amateurs, specialists and professionals forced out of their jobs by mandatory retirement rules. They've found some interesting and amusing things.

For example: If you type "editor's index to Wikipedia" in the Wikipedia search box, you see every important editing change that has been made. Among these are changes made to the records and history of politicians by people who work for them. For example, you can click on edits made by congressional staffers and find that they have edited out unfavorable information about their bosses and added extra unfavorable information about their rivals. (Whatever happened to the idea that these are public servants?)

Ah, it's a grand circus that we have before us, and you can read more about it in "Wikipedia, The Missing Manual," by John Broughton ($30 from missingmanual.com). He'll tell you what Wikipedia isn't, as well as what it is. It isn't a dictionary, though you can get one at Wiktionary.org. It isn't a collection of textbooks, but you can get those at Wikibooks. You can get travel guides at Wikitravel and how-to manuals at Wikihow.

What Wikipedia is, is beautifully described in the "Missing Manual," and you can find templates to help you create your own online articles from scratch. The author, by the way, has edited about 15,000 Wikipedia articles himself.