There are two ways to take Galtea- like there are two ways to take most IF nowadays: as a game, and as an experiment.
As a game, this offers very little. You try to come up with things to ask Galatea, and she will respond, and you can ask her more, or tell her things.
As an experinment in NPCs, this goes very deeply, and offers a lot for a writer of IF to learn when programming his own NPCs.
There is very little to do except to speak to the statue, and the statue (as far as I've seen), doesn't speak to you on her own, except for before you speak to her, kind of as a hint that this is what you're supposed to do. The author provides a good RECAP command to help you learn what topic you've covered and if there is more to cover on the subject.
The NPC is tragic, and you can't help but feel for her- which is the point, I suppose. It gives a lot to live up to in form of an individual NPC, and it's something anyone thinking of writing IF should play, if only for inspiration, and anyone interested in IF as an art form should definately look at. People who prefer games over story might be disappointed.