The technical aspect, while mostly good, isn't flawless: one puzzle is marred by what I consider a major design flaw (it turns on using an object that you're told you can't pick up), and a key object is rather confusingly described. Still, in a game this small, there's only so much that can go radically wrong, and on the whole the coding is fairly solid. Likewise, the writing is more than good enough to tell the story, and it's pretty funny in spots as well.
A Simple Theft feels like an introduction to a longer game--in particular, your boss, who's barely a character in this one, is an intriguing character who deserves more development in a longer, more in-depth game. Indeed, the ending text suggests that there's more to come: the story doesn't feel at all complete. For one thing, most of the names dropped in the introduction remain dropped--they're not explained anywhere--suggesting that the author intends to make something more of the world introduced here. The PC is worth fleshing out as well--it's intimated that you're a thief, but you don't learn anything about how you learned your trade or how you came to be apprenticed to your boss.
In short, A Simple Theft is a nice preview of what could be an intriguing full-length game. Should there be a followup, it'll certainly be worth a look.