As you said.^^
It's a story which happened during 19th-A.C. gold rush.
Buck(the dog) was stolen and taken to Alaska,and became a sled dog.
He met some bad humans and had a difficult time,almost be killed by fatigue and hunger.But later a kind man saved him and let him know what's called "love".
Unfortunately,the man died,killed by some Yeehats（native Americans）.Buck felt very sad.He killed the Yeehats and joined the wolves.
In the end of the story,he became the chief of the wolves.
Jack London wrote another novel about a wolf becoming a dog.
Also awesome.It's called "White Fang".(But it has a happy ending.)
By the way,your sentence looks weird.
It should be:
What's the theme of the book "The Call of The Wild" written by Jack London?