Book of Signs (Diadem
"Our heroes arrive on a fresh world and find a new menace - a shapeshifting sorcerer - and new friends, centaurs. The trio are discovering more about themselves and their mysterious destiny."

Originally published as part of Scholastic books, Diadem is a fantastic series about three friends traveling across dimensions in search of the truth behind the universe, and their own place in it all. The author encourages the reader to try to solve puzzles along with the characters as they traverse from one planet of the Diadem to another and includes many interesting twists on 'normal' fantasy and science fiction themes and creatures.

The first six books in the series were published consecutively in 1997, then re-published by Llewellyn in 2004. the next four were published by Llewellyn starting in 2004, and the remaining two were published by Dragonhome Books in 2012:

    Book of Names
    Book of Signs
    Book of Magic
    Book of Thunder
    Book of Earth
    Book of Nightmares
    Book of War
    Book of Oceans
    Book of Reality
    Book of Doom
    Book of Time
    Book of Games
Science fiction, Juvenile fiction, Magic, Fantasy fiction, dimensions
John Peel
John Peel (born 1954) is a British writer, best known for his TV series tie-in novels and novelisations. He has written under several pseudonyms, including "John Vincent" and "Nicholas Adams". He lives on Long Island, New York. While his wife is a US citizen, Peel continues to travel under a British passport. [source](https://en.wikipedia.org/wiki/John_Peel_(writer))