ONLY A DOZEN years ago, the world of high-stakes professional poker was an unpublicized, secretive craft. News of big games, which could be held almost anywhere, traveled quickly and informally. Reputations rose and fell, and no one really knew who was the best.

Now much of this has changed. For a month every spring hundreds of poker players--amateur and professional alike--converge, like the faithful reaffirming their religion, on Binion's Hotel and Casino in the middle of downtown Las Vegas for the annual World Series of Poker.

Anyone holding the cash buy-in can plunk down his money and choose from 13 different events. There are no other qualifications. The final four days of the tournament requires each entrant to put up $10,000 in a battle of no- limit Texas Hold 'Em. Last year, the divided prize money for this event alone totaled over $1 million. It is no wonder that professional poker, now decorated with its tournaments, trophies, and titles, has come to see itself as a kind of major league "sport."

Most serious poker players can eventually be seen at Binion's. This includes the old guard as well as a crop of aggressive newcomers. Past winners such as Johnny Moss, Amarillo Slim Preston, Doyle Brunson, Bobby Baldwin, Stu Ungar, and Jack Straus, while not exactly household names, are well known--even immortalized--in poker circles. The fast and expensive action in both the tournament and in even bigger side-games has inevitably attracted wide public attention.

A. Alvarez, an English writer and poet, made his pilgrimage to the World Series of Poker in 1981. He spent a month, mainly as an outsider and small stakes Hold 'Em player, observing the action, eavesdropping on conversations, and sometimes being frustrated and perplexed. How could one begin to understand this "different ordering of reality," where tens of thousands of dollars may be won or lost on the single turn of a card, where money, converted into plastic ammunition, means both nothing and everything?

Like several recent travel writers who have made confessions of their close encounters with unfamiliar earthly kinds, Alvarez is entranced by what he sees, but not entirely comfortable. Yet, he has woven together a thoroughly entertaining book, both perceptive and literate.

Snatches of Las Vegas' history and geography are mixed with the major attraction: the world's best poker players. He lets them speak for themselves, slurring in long, Southern drawls, or in clear Eastern tones. Many of the book's descriptions and quotes are drawn not from personal interviews but from material culled from previously published autobiographies, magazine articles, books, and press releases. These are unreferenced.

What a colorful cast of characters! Rogues and mavericks, men with strong convictions and men with adventure in their hearts, tired wives and beautiful, young women players, Texans and Jews, dreamers and losers--poker is non-discriminatory; it accepts them all.

Outsiders to the world of professional poker tend to see it as a bleak, tawdry life, or they view the winners as mangificent, untouchable icons. Alvarez has done a little of both. The setting comes off worse than the players. The stifling outside heat and impersonal air-conditioned casinos, sitting like giant toys in the desert, are a "fantasy" and a "Dreamland." Players must survive in this ugly terrain and carve out a sense of purpose and fulfillment.

Some do, but most don't. "Gambling is a romance," says one. "Gambling is a manufactured thrill," adds another. There are tales of loss, self-deception, and tragedy, whose versions are known to every gambler.

This quick Cook's tour into the land of professional poker is not without its shortcomings. Little is said of the essential social ties between professional poker players, ties that have created lifelong bonds and immense enmities. We are only given a glimpse of the very top of the pecking order. This is an order that is not easily discoverable and one built on playing skills, fluid bankrolls, borrowing power, reputations, and often hidden transactions of lending and indebtedness. These are the critical ingredients that define informal cliques and make much of the at- the-table play understandable.

And what of the daily grind during the rest of the year when the television cameras and groupies are gone? Ah, but that would be a different book.

A philosophical old poker player once said that anyone who spent his time reading (or writing!) a book about poker, rather than playing the game, must be sightly misguided. But if one should make the time, even between anteing up, to be drawn towards poker's fascinating annual rites of renewal and self-identity, The Biggest Game in Town offers the best deal.