“You know how teachers tell you the magic word is 'please'? That's not true. The magic word is 'puke'. It will get you out of class faster than anything else.”

Power Of The Plus Factor (1987)

Part 3, Chapter 3 (p. 128)
A Door into Ocean (1986)

Source: Grave Peril

Variant: It doesn't stop being magic just because you know how it works.
Source: A Hat Full of Sky

Source: Skulduggery Pleasant

Source: City of Lost Souls

Equinox (1973)
Context: It is a magic book. Words mean things. When you put them together they speak. Yes, sometimes they flatten out and nothing they say is real, and that is one kind of magic. But sometimes a vision will rip up from them and shriek and clank wings clear as the sweat smudge on the paper under your thumb. And that is another kind. (p. 163)

Source: The Wee Free Men

Source: Secrets of Eden