The Between Two Worlds blog recently pointed me to Mortimer Adler’s essay, entitled "How to Mark a Book."  Adler was an American philosopher & writer who loved ancient classics.  Some of his books, including "How to Read a Book", became popular bestsellers.

The gist of How to Mark a Book is that there are two kinds of ‘owning’…You own a book when you buy it, but you don’t really own it till you internalize it.  Adler sets forth a great case for writing in the books you own (in the first sense), so that you really own them (in the second sense).

His writing is very clear & enjoyable and he gives suggestions on how to write in a book, what to write and why to write.  The essay is short and well worth reading through.  Here’s a couple brief quotes to tantalize you…

• I contend, quite bluntly, that marking up a book is not an act of mutilation but of love. You shouldn’t mark up a book which isn’t yours.  Librarians (or your friends) who lend you books expect you to keep them clean, and you should. If you decide that I am right about the usefulness of marking books, you will have to buy them.
  
  
• There are three kinds of book owners. The first
  has all the standard sets and best sellers —
  unread, untouched. (This deluded individual owns
  woodpulp and ink, not books.) The second has a
  great many books — a few of them read through,
  most of them dipped into, but all of them as clean
  and shiny as the day they were bought. (This person
  would probably like to make books his own, but is
  restrained by a false respect for their physical
  appearance.) The third has a few books or many —
  every one of them dog-eared and dilapidated, shaken
  and loosened by continual use, marked and scribbled
  in from front to back. (This man owns books.)