The answer is D, the last one. D is the only sentence that makes a point of stating the author's opinions of books, while the others placed their focus elsewhere.
The way the question is written is a bit confusing. To anyone else wishing to answer, I believe it goes like this:
A. No matter how many were printed, there was only one copy like mine
B. I stole - well, borrowed - the shoe box of letters.
C. I'm glad I'm a "romantic soul," that my work is worthwhile.
D. I cherished the musty smell of the paper, the permanence of the deep black ink.
