Are you familiar with the "Toddler Laws of Property"?
If it's in my hand, it's mine.
If it looks like mine, it's mine.
If I played with it a while ago, it's mine.
If I think it's min, it's mine.
Toddlers have to be taught to share. You're off to a good start in that he will actually hand you a toy - but it's mostly because he knows you will hand it back. He will be 3 before he is good at sharing toys and even then you should make certain any special favorites are put away before any other kids come over.
Are there books? Tons.
Also, point out every time you share or take turns... waiting in line at the store, waiting at a stop light, giving him some of what you are eating. There are lots of times you share each day.
at 4:35 PM on Jun. 5, 2009