This is a really solidly implemented short game, and undoubtedly enjoyable to play. Ultimately, however, I found it unsatisfying, and wondered why. I think there are two reasons.
First, I think the story is neither convincing nor charming. It's unconvincing in the sense that the characters are not psychologically convincing, the plot is vastly implausible, and the actions of the characters are not realistically motivated. None of this would matter if the story was told as a charming or even an intriguing espionage tale with period charm, a la Buchan or Fleming. But in the final analysis it lacks this sort of spirit or charm.
Secondly, in terms of its interactive characteristics, the game is rather manipulative. It has clear, even dicatorial, ideas about what you should do, where you should go, what you should be asking whom. It will nag you and cajole you, and ultimately even force you to do as it wishes. There's a lot of rather pointless searching for some object the game has just decided you must have. For me, at least, this gets tiresome--not so much a question of guessing the verb, as guessing the noun, as one tries to work out what object might repay searching. Even with a very solidly and deeply-implemented environment this is not all that enjoyable.
This leaves what is most interesting about the game, which is the ability to control person and tense. But, interesting as this is (and impressive as the implementation is) it's not interesting enough to carry the whole game.
So, certainly a game worth playing, both to experiment with tenses, and for its intrinsic interest. But not, to my mind, truly compelling.