Here, courtesy of the Tappin Book Mine, are the needed instructions:
unopened: A state where the book's pages at the fore edge and/or top are still joined from the folding. This cannot occur if the book has been properly cut(See: uncut). At one time many books were issued unopened, and it is not uncommon to find older books still in this pristine state.
A rare book that is unopened may be considerably more valuable than that same book opened. Therefore, one should consider carefully before opening a book. Of course, you cannot read a book that is unopened, at least not in its entirety.
NOTE: If you wish to "Open" a book in order to read it, DO NOT USE A VERY SHARP BLADE TO OPEN IT. Use something like a letter opener, and gently TEAR the fold, DO NOT CUT THE FOLD. You may find it useful to sharpen the crease at the fold before you attempt to open it. Don't use your finger to open a book, either. That is guaranteed to result in a book that is "Badly Opened", with rough, ragged tears that extend into the page. At one time, Gentlemen carried a "Paperknife" to open books.