I love buying used books and finding that someone has written in them—I get to see what someone else thought was important or moving or awful or stupid. I love the sometimes snotty messages that a reader just could not refrain from noting, or perhaps a personal comment that shows a glimpse into a stranger’s heart, a glimpse that might well be one of the few remembrances of that person. Even the occasional shopping list or notes for a speech or a child’s handwriting practice can turn an unexceptional book into a lost but tangible place in someone’s life.
It has only been in the past few decades that marginalia has come to be valued—in the history of the book, collectors and libraries have generally gone to great lengths to scrub all marginalia clean from books, much to the dismay of book historians today. Not long ago the British Library in London purchased a second copy of a rare treatise of Galileo’s specifically because it has marginalia in three different hands. These are not notes from Galileo himself—the library did not know who wrote the notes nor what they said when they bought the book, but those annotations were finally being valued as a “contemporary response” to the book.
Reading is also writing, in that you become a part of your book; thus both you and the book become part of the historical record of us humans on this wee planet. The Wikipedia page on marginalia has an interesting list of famous writers well known for their marginal notes. Even if you're not famous, infuse your Shakespeare reading editions with a trace of your humanity!
Perhaps you have checked out the page on iReadShakespeare.org about writing in your own books. I hope so—and I hope that you scribble away in your Shakespeare editions. ;-)
“The book is to be engaged, digested, and re-read.”
—Heidi Brayman Hackel, Reading Material in Early Modern England