Under the Magician's Spell (Give Yourself Goosebumps #7) by R.L. Stine - Vintage Paperback

Reader beware--you choose the scare! 

You, and your little sister, and your best friend just found a new magic shop at the mall. The man inside calls himself the Magician. He's pretty creepy. Before you know it, your little sister runs out of the shop with his book of magic spells.

If you read one of the spells, you find yourself in the magician's workshop. Suddenly you are part of a magic act. You are forced onstage, about to be sliced into a million pieces!

If the three bullies from the school grab the book, you must find it before the magician makes your sister disappear...forever!

The choice is yours in this scary GOOSEBUMPS adventure that's packed with over 20 super-spooky endings!"