SunshineonMe, Mamitt, BethS, mrsmig, PandaMan, thank you all so much for your responses! I really do appreciate your advice.
Yes, it's MG.
However, my protagonist is thirteen, so I like to think my specific target audience is more on the older side.
I tried very hard to establish Adam's wry personality as soon as possible while simultaneously introducing the problem that jump-starts the conflict, but I see now that it's too repetitive and probably will annoy my readers more than intrigue them (especially since I actually
still rambled on about nothing after these first sentences). Thank you all for pointing that out.
Here is my first attempt at a re-write:
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As the whole school screamed and stared, Adam Bartholomew casually observed that he had once again found himself in exactly the wrong place at exactly the wrong time.
No surprise there of course, but this time was different.
Before him loomed a
rather pompous old mirror, stretching floor-to-ceiling against the wall at the top of the Grand Staircase,
(maybe split the sentence here and change which to It) which seemed to have
malfunctioned somehow so that Adam (who was most definitely alive and well, mind you)
(I think commas work better than a pair of parenthesis, but maybe that's just me) had vanished.
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I'm hoping this sheds a little more light on the action and setting as well as show that Adam's first response to a problematic encounter is laughably analytical considering the absurdity of the situation, but I'm afraid it might be too wordy.
I also could be over-thinking things, as usual.
Thank you all again for your thoughts!