I like the question about the textbooks. It's in the same vein as the questions about the packed boxes and the pictures not hanging on the wall.
We don't know when she packed up the room. Whether she packed up the room JUST before the trip, or before leaving for the winter break, we don't know why she packed. With the exception of trip-related items and the alcohol, we can't be SURE she took anything deliberately, or just tossed her books in there after a study session or left other stuff in the car because it's hard to clean a car in the winter (I teach--my car always has books, jackets, and other stuff in it.)
But there is this powerful urge to make all of these points into a coherent narrative. It's clear something was bothering Maura, but there's a lot of evidence (needing no interpretation) that she was in reasonable contact with people and taking care of routine business. She talked to the boyfriend and texted him; she picked up the insurance papers as she had told her father she would. She emailed her instructors and employer (she didn't just blow off class or quit the job). She tried to make reservations. She packed for the trip. None of this looks like suicide to me.
And that is what makes the implication by Scarinza so disturbing-- that an old note FROM her boyfriend was a note left BY Maura with her just-packed stuff. He wouldn't be the first LE officer to be happy to close a case as suicide (even if it wasn't). But I wonder about the haste to do that, to close the case in Massachusetts (as if the important evidence were there, and not at the actual site at which she disappeared) without EVER checking into the calls she made to NH, without talking to the very person who might have been told why she was making the trip--the person she talked to about renting a condo. It took her boyfriend's mother to make that call long, long, after the fact, and by then the condo owner didn't recall talking to Maura. So at the very least, it was a shoddy investigation from the start. Incompetence? Ego? Indifference? Covering up for the local tourist resorts? or worse? I have no idea.