"The Last Necronomicon" by Larry Niven

There has never been anything like the student riots of 1973, before or since.

1973 was the year Ace brought out the paperback version of the NECRONOMICON. By February there were stacks of the slim volume in every bookstore in America. Ballantine immediately brought out an "authorized version" at a slightly higher price. The Ballantine version included a George Bar cover (the reproduction techniques did not satisfy George Barr), a short introduction by the author, the mad Arab Abdul Alhazred (obtained by on of the simpler spells in the Necronomicon), and a much longer introduction by Lin Carter, which bulked out the book considerably.

Unfortunately (fortunately?) neither edition was particularly accurate. The Ace version had more misprints; but most of the errors were due to mistranslations accumulated through several languages and several centuries of time. The publishers and distributors could not possibly have guessed how many millions of readers would try to use the spells in the old book. Otherwise they might have taken more care with the more dangerous spells, Or they might have burned the book.

By July, every student revolutionary in the U.S.A. must have had a copy.

Strange things happened during the Peace Riots at Miskatonic University. Professors disappeared. So did Long Hall, with all of it's students. Every professor who attended the July 23 faculty meeting was turned into a giant frog. And the students who, on July 29, forceably occupied the Administration Building with the aid of a toothy, shapeless, gigantic ally, vanished from the Administrative Building along with that ally, leaving unbelievable quantities of blood behind.

Student leaders accused the faculty of using counterspells. They were wrong. The faculty did not themselves try to use the Necronomicon until August 4, because August 4 was the day they and the National Guard forced Their way into the Library. The Faculty had enough sense to use the hardback editions. All the previous casualties among the students must've attributed to spells which misfired.

There were misfirings among the counterspells, too.

In general, the beings summoned by the students were the Great Old Ones, Cthulhu and Dagon and Yig and the others who were also revolutionaries of a sort. Those the students called the "establishment" appropriately summoned the Elder Gods-and found them even more difficult to control. Of those combatants who survived the Miskatonic Riots, these are typical:

The National Guardsman who threw down his gun and proceeded to worship Cthulhu. The huge, ancient, inhuman priest seemed to accept the Guardsman's worship; at any rate, he turned away.

The Sophomore who threw rocks at Nyarlathotep until the Crawling Chaos broke into a great booming laughter and let him go, after making some humorous changes in the Sophomore's physiology. The Sophomore is now a Senior and a hermaphrodite who wishes to remain anonymous.