The more hotspots, the better. Not just generic messages though. If I see something in a game, the protagonist should be able to see it, touch it, smell it, etc. To me, it does not matter if the object in question has any real use. Adventure games are meant to be explored. It also helps give the player a insight on how the protagonist views the world around him. If you kept it to a bare minimum you might as well just have objects you can only use in the game, accompanied with a in game walkthrough telling you what you need, where you need it, and what you need it for.
Of course I don't mean that ever little book in a bookshelf needs a separate description or interaction. But you get the idea.
Of course I don't mean that ever little book in a bookshelf needs a separate description or interaction. But you get the idea.