The Oxford English Dictionary.
It calls itself "the definitive record of the English Language," and rightly so. If you're a writer, a poet, or just a "word-lover" (first documented usage in 1857, says the OED), you might lose yourself in it for awhile. Possibly to the annoyance of those around you who don't quite share your enthusiasm. (Ahem.)
For those unfamiliar with the OED, here is its claim to fame:
"As a historical dictionary, the OED is very different from those of current English, in which the focus is on present-day meanings. You'll still find these in the OED, but you'll also find the history of individual words, and of the language — traced through 3 million quotations, from classic literature and specialist periodicals to film scripts and cookery books."
The writer David Foster Wallace (1962 - 2008)
"No really serious writer should be without an OED, whether it's bought or stolen or hacked into the online version of or whatever you need to do. Nothing else comes close."
We agree with part
And anyway, no hacking necessary. Our libraries subscribe to the OED online
so that you'll always have this classic resource at your fingertips — in the library, at home, or about town. Start here
and select "Begin Using This Tool." Once you're on the OED website, select "Sign in" and enter your Jones Library card number.
Of course, if you'd prefer to flip through the physical, hold-it-in-your-hand, printed and bound OED, just visit our Reference Room. We've got 17 volumes worth on the shelf.
In closing, you're welcome.