Should you write in your books?

Some people would sooner write on a museum wall than in a paperback. Others read with a pen behind the ear and leave every book looking like a marked exam. Both camps are right about something. The useful question is not whether writing in books is allowed, but what you want the book to do for you after you close it.

The case for writing in the margins

A margin note is a record of a conversation. You read a line, you agree, you object, you are reminded of something, and for a second you answer back. Write that answer down and the book holds a trace of your thinking, not just the author's.

That trace is surprisingly valuable later. Open a book you annotated five years ago and you meet two people: the author and a younger you, arguing in pencil. It is one of the quiet pleasures of rereading. Marks also make a book usable. When you want to find the passage about friendship, you flip to the asterisk rather than skimming two hundred pages.

And writing slows you down in a good way. You cannot comment on something you skimmed.

How to annotate without wrecking a book

• Use a soft pencil. It is quiet on the page, erasable and does not bleed through thin paper. Highlighter pens look emphatic and age badly; ballpoint is permanent and tends to show through.
• Write words, not just lines. Underlining a whole paragraph tells your future self almost nothing. A two-word note, "disagree: why?" or "same as ch. 2", tells you exactly why you stopped.
• Mark less than you want to. If every page is underlined, nothing is. A good rule is a handful of marks per chapter.
• Build a tiny code. A vertical line for "important", a question mark for "not convinced", an exclamation mark for "lovely sentence". Keep it the same across every book.
• Use the back pages. The blank pages at the end are perfect for an index of your own: a page number and a few words for each passage you want to find again.
• Date the first page. Just the month and year, and maybe where you were. Ten years on, it is the note you will enjoy most.

Books that invite a pencil

Some books practically ask for it. Essays, letters and books of ideas, where an author is talking to you, are the natural home of marginalia. A selection of Seneca's letters to his friend Lucilius, written in his last years, is a good example: each letter is short, opinionated and addressed to someone, which makes replying in the margin feel natural. See our page on Seneca's Letters from a Stoic.

Novels are a different matter. A pencil can pull you out of a story. Many readers keep fiction clean the first time and annotate on the second read, when they already know what happens and are reading for how it is done.

The case for clean copies

There are good reasons to leave a book untouched:

• It is not yours. Library books, borrowed books and shared copies stay clean, always. Your friend does not want your thoughts on chapter four, however sharp.
• It is special. A first edition, a signed copy, a book with beautiful paper or plates, or a family copy with someone else's history in it.
• You plan to pass it on. Some readers love finding a stranger's notes in a second-hand book; others find it maddening.
• You read better without it. If stopping to mark breaks the spell for you, don't.

For all of these, the workaround is simple. Use a slip of paper as a bookmark and write on that. Keep a small notebook alongside the book. Or copy the passages you love into one notebook for everything you read, which is the old idea of the commonplace book.