"When I was a youngster, there was no basic spell book to give a beginner witch like myself the clear and simple instructions that would have made magic a much less mysterious process."
-- Miranda Goshawk (BOS)
Miranda Goshawk, who lived some two hundred years ago, grew up searching for a good, simple book of spells. Goshawk had a lot of older sisters who teased her by telling her the wrong incantations for spells as they were growing up. As Miranda put it, “Hand me down robes are merely embarrassing — hand me down spells can be dangerous.” When she eventually realized that no straightforward spell resource existed, she wrote one herself: the famous Book of Spells, now housed in the Restricted Section of the Hogwarts library.
Eight older sisters - including Diadema, Romilda, and Tangwystl - who repeatedly attempted to give Miranda the wrong incantations for spells. After publishing Book of Spells, Miranda printed special editions with misprints for her sisters, which led to several mishaps like Romilda gaining a tail. In the forward of Book of Spells, Miranda claims they are all friends now (BoS).
Other canon notes and references
The author Miranda Goshawk is listed on the Famous Wizard cards as having been born in 1921 (FW), which doesn't match with the date given for the original creation of The Book of Spells ("two-hundred years old", JKR). How do we rectify these discrepancies? Perhaps the original Miranda Goshawk lived two-hundred years ago and wrote The Book of Spells, while her descendant, also named Miranda Goshawk and born in 1921, revised, expanded, and updated the venerable book into a book series with one volume for each year of a student's education. Alternatively, the Book of Spells may be 200 years old dated from some time in the future after 2121 (or, realistically, after 2138 to account for Goshawk's age at the time of publication) instead of dated from the June 2012 of the Book of Spells release.
goshawk = Old English for a large, short-winged hawk once used in falconry
Miranda = Latin for 'worthy of wonder.' Also the name of the daughter of Prospero the magician in Shakespeare's "The Tempest"