Here's one for you hardened narratologists wanting to push theory into practice.

BladeEngine is an interactive novel authoring and presentation engine from CuriousFactory and Buredo. It's freely downloadable (though not open source) for the Windows platform here. As a Linux user I haven't been able to try it. If you do and feel like writing a little review of your experiences, drop us a line and we'll post it.

Says the site:

What is Visual Novel?

Most Visual Novels have multiple storylines and many endings; the gameplay mechanic in these cases typically consists of intermittent multiple-choice decision points, where the player selects a direction in which to take the game. This style of gameplay has been compared to the Choose Your Own Adventure novels. Most, however, strive for a higher level of plot and character depth than the aforementioned series of interactive children's books. These can be more closely compared to story-driven interactive fiction.

Content and Genre of Visual Novel

In the West, there is a stereotype of: "Visual Novel = Dating Sim Game = Hentai", but that is wrong. Visual Novels CAN be Dating Sim games, Ren'ai games, Bishoujo games but also can be Sci-Fi, Fantasy, Adventure and Horror Fiction games, or anything that the user's creativity comes up with.