How many books are there in the thirty-nine clues?

There are ten books- 1the maze of bones, 2one false note, 3the sWord thief,4beyond the grave,5the black circle, 6in too deep, 7the viper's next, 8the emperor's code, 9storm warning, 10 into the gauntlet. There's going to be another book called the cahill book of black secrets.