Although your manager wants you to keep busy, it will be surprising if the company can keep you at all. There is no excuse for this type of treatment. Even if there was a major emergency, your manager owed you an explanation and a back-up plan.
However, if you quit impulsively right now, you will most likely throw yourself back into the labor market, and year-end is not a great time to be shopping for a job. Be fair to yourself and at least wait until your manager returns and see if you can find any of the compelling reasons that led you to join this company in the first place.
In the meantime, you should try to get your office in shape and meet as many key people as possible. This will help you learn more about the company and whether you truly have or want a future in it. You might even find an ad hoc mentor as you travel up and down the halls.
When your manager returns, you should discuss what happened here, but try to do so through questions rather than a flood of negative comments. His answers will tell you if you selected a questionable company.
| 
