In this one volume are clear-cut explanations of various expressions of beer. The book decodes traditional styles that, even though they have been around for centuries, have not been well understood or explained, as well as styles that have been rejuvenated or invented in the last 20 years, like sour beers, barrel-aged beers and double I.P.A.’s. There are profiles of noted and historical figures, and discussions of controversies over nomenclature. Brewing techniques are broken down, some recognizable, like dry-hopping, and some that may be of interest only to brewers, like decoction, an intensive method of blending water and grains to begin the brewing. For browsers, the book is a treasure trove.

Much has been written about beer in the last 20 years, but until the “Companion” no book has ever tried to consolidate the extent of what is known about how beer is made, categorized and consumed. Much of what we think we know about beer qualifies as conventional wisdom, some of which is called into question. For example, it may not be true that two different strains of yeast account for the differences between ales and lagers.

“When I was a kid, a dinosaur was a dinosaur and Pluto was a planet,” Mr. Oliver said. “Now, we think a bird is a descendant of a dinosaur, and Pluto’s just a big rock.”

Over the course of the meal we drank some beautiful beers that made great combinations with the food. A spicy, vibrant Saison Deluxe from Southampton Ales and Lagers was paired with a dish that mimicked a Long Island clambake, an exercise in conceptual localism, while an 1809 Berliner Weisse, tart but complex with a soft roundness to it, contrasted beautifully with luxurious langoustines in a fruity sweet and sour sauce. Nowadays, most people think of Berliner Weisses as tart, acidic wheat beers made drinkable by adding sweet, fruity syrup. The 1809 was created by Fritz Briem, a German professor whose research indicated that 19th-century versions did not require sweet additions to be palatable.

“You would never think of adding syrup to this,” Mr. Oliver said. Professor Briem, incidentally, wrote the entry on Berliner Weisse in the “Companion.”

As beer programs like Eleven Madison’s and volumes like the “Oxford Companion” are partly an effort to portray beer in all its multifaceted glories, some fear that a consequence will be a rise in the same sort of anxieties and pretentiousness that plague and intimidate wine consumers.

I think this fear is overstated. Beer consumers are a far more confident lot than wine consumers. They’re at ease with beer, mostly because they’ve had a solid grounding in their subject, unlike wine consumers who’ve been brainwashed into believing they must be educated or taught how to “appreciate” wine before they can enjoy it. The “Oxford Companion” is simply a wonderful resource for what, even when it’s complex, unusual, unfamiliar or strikingly different, is still just beer, regardless of how it is dressed up.