There are a lot of Twine games out there, and it does a lot of cool things and is really popular.
My main concern with Twine is I don't like the way the default output looks. I know you can change it, and I know you can do all kinds of tricks, but my main goal is readability.
I've discovered AXMA Storymaker, which is a whole lot like Twine, but is wrapped up in one nice package similar to Inform. It also seems to have a lot of built in features that you have to script by hand in Twine like real-time timers and such. I think currently you have to use a separate compiler for Twine, and AXMA has one button that quickly compiles and lets you test the story which is really nice. Disadvantage for some: you cannot tweak the HTML in the free version, but for me that's a plus. You do get to adjust the text and choose white, sepia, or white on black similar to an e-book reader though, and the player can change this as well.
The output is much more book-like than webpage-like. The output is almost similar to Inklewriter (which I also love but there you cannot divorce your writing from the website as a standalone file).
There's a paid version which takes the tiny "Made with Axma Storymaker off the bottom of earh page, and allows you to tweak the HTML to your satisfaction, and customize the UI available in the end-user reading interface. Otherwise, the documentation states that you are free to do what you want with stories made by AXMA whether made with the free or paid version, including release them commercially.
AXMA will also publish to Epub...I'm not familiar with this, but a lot of the fancy macro trickery won't happen in Epub, so if you use that you have to write a slightly more straighforward narrative without macros like a vanilla CYOA. I am not sure if that means no variables either, but I need to experiment further...if I need to make an Epub for anything.
I've been playing with it and trying to discover what kind of story to do with it. The programmers are Russian, and there is a rather active google group where the creator (or a spokesman for the creator) is quite prompt to answer questions.