Admittedly I am not a huge fan of poetry, especially free verse. Though if the imagery is evocative I can get lost in it from time to time. Unfortunately, the design of The Space Under the Window, while making for an easy game, results in an unsatisfying poetry reading.
In a sense, this structure of play feels like a precursor to Twine, only one has to guess at the keywords instead of clicking on them. And it's hard to get lost in poetry when the parser doesn't respond to half of what you type. It's very difficulty to predict what keywords will trigger a new path or bring you back to an old one, and also difficult to predict where the story will go. There are no puzzles to elicit satisfaction from all the keyword guessing so it's all a bit underwhelming.
That said, it's an intriguing (and short!) parser experiment from one of IF's greatest authors.