Does anyone have helpful advice or can you recommend a good book for a single mother an who has just started dating again, her only son is eleven years old.

The son hates his mother's new boyfriend and is so angry that she is going out with him that he says he wants to kill him. The son is very emotional about the situation and believes that the only solution is for the dating to stop.
 
The mother doesn't want to begin behaviours that will encourage the son to think he can control what his mother does and with whom but she doesn't want to get into a power struggle, she wants a win-win situation for her and her son but she doesn't know how to go about it.

Have any of you had experience of a similar situation and how did you deal with it?

Ciao, Ozzzy