The Most Badass Reference Work In the World, the printed Oxford English Dictionary is twenty ponderous volumes long. You can buy it in leather. You can get a two-volume compact edition that comes with its own magnifying glass, because they just shrank the plates for the twenty-volume edition down four to a page!

It's No Ordinary Dictionary. Each entry shows you the word's history and each major definition and minor definition since its first appearance in written word. These tens of thousands of minor definitions each list the first known occurrence of the word, the progression of its use through the centuries, and if the definition is archaic--that is, no longer in use--the last known occurrence of the word in printed text. You get all that plus references to other obscure related words and all the content you'd expect in less weighty dictionaries, too.

Let's say you had to write a three-page paper on a word, like "spell". The OED dedicates a page and a half to this one word's meanings, from the archaic "spelling" of an sentence--meaning to say each word, one after the other--to the conventional spelling of a word, without leaving off the still-used less-recent additions like to cast a spell on someone. The OED shows that spell in all its forms has meant spoken power, and there's your thesis.

Day-to-day, its users find new words and phrases that have "gone glimmering"--that have been lost.

There's a horde of history behind the OED. A bestselling book, the Professor and the Madman, documents the integral contributions of a man in an insane asylum who helped find many of the examples needed for the creation of the original OED.