I wonder what the market is for text adventure games. Does it still exist? I know some people are selling games they make in Inform7, but I couldn't tell you how many copies have been sold.

Mud games still work pretty well, but their biggest sales are items, which add to the game. There is Gem Stone, which is free, but they also have other paid games where the user can't play without paying a fee. They're also some of the best text games on the net though.

Adventure Books can't really compare, because they do have graphics. In fact the book itself is graphics, and then there's pictures inside with text. Also animated 3D dice.

I wish single player text games had a market. If they did I would go into production, and not worry about finding an artist and support writer for the game I'd like to make :P