I came accross a great book today, its called "My New Baby" (by Jeanette Rowe)
and its essentially a very very simple story book about the new baby in the family. I gather you read it to the older sibling. What i loved about it is that there's one page which says:

"My new baby..... loves dinner time"

and the illustration shows the mother breastfeeding! Thought this was fabulous! Will be reading it to DS when i'm pregnant with our next baby.