Now the book that the MC possess is a bit special. It allows him to travel between worlds and alternate dimensions, and to become the Master of anything in those Worlds.

Now it sounds like the MC could very well be the master of the world or the master of a stick....Which is the case !

Everytime he goes to a world, or comes back to another he has the choice to become the Master of a random thing and completely change it however he wants. Like say he became the Master of the Bleach World and decided to wipe out all the Quincies, he could.

If he became the master of a sword, he could change it's abilities with the help of the Book. Though of course the Book won't allow him to randomly change stuff for free. To do that he will need points that he can get by simply completing the quests that the book will give him.

The power of the Master of All has an infinity of uses, so if you've got any ideas, you can simply write them down in the comments. However the story will start with something relatively small, as the MC needs to get used to his power.