I have a 21 year old a 19 year old a 17 year old a 15 year old a 13 year old and an 11 year old. I don't get why people think having teen-agers is hard. Mine give me no trouble at all.
The bookshelf thing... get the kind of bookcase that has doored cupboards on the bottom, and install baby-proof latches, and/or install doors on your existing shelves. Other than that, move all the books up, and use the space at the bottom for toys.
And yes, DO make sure the bookcases are properly secured.
I used to have a chewed on thesaurus around here. When people saw it, they assumed the dog had been at it. Uh.... no. Dogs have sharper teeth.