Hidden away in the local library, a sorcerer's book casts an evil spell in the next novel in the Johnny Dixon Series.

Johnny Dixon and his best friend, Fergie, are whiling away a rainy day at the Duston Heights library when Johnny asks a screwy question: "What's the last book in the library?" After Johnny goes home, Fergie decides to find out. There, under number 999.99, he finds a very peculiar tome, The Book of True Wishes, which is all about Fergie's favorite subject: himself. The book knows Fergie's name and promises him everything he ever wanted, which means he is about to forget a very important rule: be careful what you wish for.

When the book puts Fergie under the spell of a mad old wizard, Johnny and his friend Professor Childermass will do whatever it takes to break the book's hold and save their friend.