Just to add to this recommendation, Aaron Reed's Blue Lacuna is one of the best pieces of interactive fiction I've read/played. It's practically novel-length, well-written, contains some interesting puzzles to solve (or skip, if that's not your jam), and has some pretty rich world-building. And it's free.

Also, for those interested in interactive fiction, Andrew Plotkin's long-delayed commercial IF Hadean Lands is finally available. I haven't yet finished it, so I can't offer a fully informed recommendation, but I'm enjoying it so far. It's very puzzle-dense, and a lot of the puzzles center around its extremely elaborate alchemy system. Figuring out how alchemy works in the game has a sort of HPMOR-esque "apply rationalist methods to a magical system" feel. Avoid if you don't like having to sort through a deluge of information in order to solve puzzles and make progress.

And, finally, if you are unfamiliar with Plotkin's work, I highly highly recommend Spider and Web, which is free to play. It also has the theme of figuring out how things work in an almost-but-not-quite-familiar setting (technological rather than magical, this time around). It has a very clever narrative hook, where you're a captured spy being inerrogated and the game is your (often unreliable) account of what happened. And it has probably the best narrative-integrated puzzle in any game I've played (you'll know it when you see it -- or solve it, rather).

You'll need to install a Z-code interpreter like Gargoyle to play any of these.