Time travel books
Time travel can be very exciting, even if you are only going to play with some new friends. But who do they think they are playing with? A ghost?
If you just go back in time to play with your friends, that is probably alright, maybe you won't initiate any great chain of events that will have repercussions in the future. But what happens if things get out of control? And can you travel back in time to change events? Have a look at some of these books. You might also like to look at my article 'Time travel'.