This game only takes 10-15 to playthrough once, and I recommend you play through it multiple times. It is useful in getting a new player acclimated to the mechanics of IF, including the frustrating parts like being told you can't do something because of a minor detail you forgot (Spoiler - click to show) like having to specify to take your watch off before getting in the shower.
My first playthrough was over unexpectedly and anticlimactically, but I got to have some fun on subsequent playthroughs. After playing it by yourself a couple times I recommend reading a walkthrough to learn all its secrets. This will help give you an idea of what to look for in future parser-based IF games you might play.