The adventure continues...

Nathaniel Hancock and his cousin Tommy are off on another thrilling adventure in the magical Inkworld. With the help of their great-grandfather's mysterious book, The Masterpiece, and a band of powerful Elves, the boys must track down the missing portals that connect their world to the Inkworld. But these hidden passages could be anywhere—and finding them is only the beginning.
As they search, a shadowy force from a dark side of the Inkworld rises to stop them. Strange creatures attack at every turn, hinting that other Pen Wielders may be at work.
Each new revelation only raises new questions. Who is the mysterious Keeper of Keys, and what secrets do they hold? Do they open locked doors? Are there more magical pens? Where are the dark forces coming from?
Their adventure leads to a dramatic showdown in London and the city is left splattered with ink and the real world begins to notice that something magical is happening. With danger closing in, Nathaniel, Tommy, and their Elven friends must summon all their courage to protect both worlds—and save the Inkworld they love.

It has been compared to The Neverending Story, The Chronicles of Narnia And Inkheart. It also is similar to The Phantom Tollbooth with its wordplay.