Brewer's Dictionary of Phrase and Fable (Paperback) by Anon

from RShelton

My undated hardcover copy has been invaluable in research and writing. This reference book has nearly every entry you could think of, from famous people to plants to humorous linguistic corruptions of a popular 17th century Spanish wine ("Peter-see-me").

from tuckerresearch

The Wikipedia of the previous generations, a delightful compendium of trivia, essential knowledge, mythology, common phrases, and on and on and on. Nothing but interesting tidbits of knowledge to get lost in for long periods of time. Skews a bit to the British and the Victorian, but the updaters ...

from overthemoon

something that helps me greatly in the office

from KerrvilleCate

Remarkable book and very useful if you write.

from reading_fox

Fascinating links between everyday phrases and history, not actually useful as such, but its easy to lose a morning flicking from article to article. Occasionally useful as a crossword reference!