I was still relatively junior when that dumb book came out. I bought it, started reading it eagerly, started getting bored, finished it, sold it to a bookstore. Bookstores didn't usually buy used software books because nobody wanted anything more than a month old, but they took it because it was the going thing.
The book spawned a cult. Development leads would carry it down the hall like a religious tome, wearing the fixed thousand-mile stare of the Newly Enlightened.
I didn't think it was all that great but since its release I see every small scrap of code shoehorned intro one Pattern™ or another.
The only one I ever refer to is the singleton.
Years before one James Coplien had written Advanced C++ Programming Styles and Idioms, a much better book that managed to make the same observations in much cleaner text, but it was probably his title specifying C++, which most developers couldn't handle, that kept it from taking its rightful place as one of software's revolutionary tomes.
Glad I'm finally not the only one who's had it up to here with "patterns."