Bjørn Rasmussen 
Bruce The Karate Dog [EPUB ebook] 

Paco gets a puppy on his 7th birthday. The dog grows up and completely takes over the leadership from him. What can Paco do to keep the fierce dog? He gets complaints about the dog that has bitten a schoolmate, and he is afraid that the dog will be killed because of this.
Paco is very fond of the dog, who is his only companion, and he will do everything required to keep it. Paco also has problems in his school, where his classmates bully him because he is so small.
The dog and Paco help each other to solve their problems.