5 is the answer. 4 have been released already; they are as followed Raven's Gate, Evil Star, Nightrise, and Necropolis.The fifth book is not yet known.
Necropolis
There are only 4 books, and the 4th is out, and there shall be no more books because there are 2 new gatekeepers in book 3
The Gatekeepers has 292 pages.
The Gatekeepers was released on 02/01/2013.
The Production Budget for The Gatekeepers was $1,500,000.
There are five books in "The Gatekeepers" series by Anthony Horowitz, with the first book titled "Raven's Gate."
The ISBN of The Gatekeepers is 0-670-03135-6.
The Gatekeeper was created in 2004.
There are exTactly 6 books. In order they are: house of dark shawdows, watcher in the woods, gatekeepers, timescape, whirlwind, and frenzy. The author might be making up more books soon but is working on another book which is not in the series
The Gatekeepers grossed $2,408,553 worldwide.
The Gatekeepers grossed $2,408,553 in the domestic market.
St. Louis GateKeepers was created in 2009-11.