The founding classic of modern editing practice.
From the wiki
The Elements of Style is an American English writing style guide in numerous editions. The original was written by William Strunk Jr. in 1918, and it was published by Harcourt in 1920, comprising eight "elementary rules of usage," ten "elementary principles of composition," "a few matters of form," a list of 49 "words and expressions commonly misused," and a list of 57 "words often misspelled
Strunk concentrated on the cultivation of good writing and composition; the original 1918 edition exhorted writers to "omit needless words," use the active voice, and employ parallelism appropriately.