Where did you get this average? Based on your experience? If it is based on your experience then it cant be called as average in general. If I can say based on my own experience then the bonus round in Book of Dead and other similar types slot games such as Rise of Merlin and Legacy of Dead is better than the other slot games. I'm starting to use Live RTP global statistic when I want to play a specific slot game. If the Live RTP shows lower percentage than its original RTP then I would not play the game.