* Books You Haven't Read;
  * Books You Needn't Read;
  * Books Made For Purposes Other Than Reading;
  * Books Read Even Before You Open Them Since They Belong To The Category Of Books Read Before Being Written;
  * Books That If You Had More Than One Life You Would Certainly Also Read But Unfortunately Your Days Are Numbered;
  * Books You Mean to Read But There Are Others You Must Read First;
  * Books Too Expensive Now And You'll Wait Till They're Remaindered;
  * Books ditto When They Come Out In Paperback;
  * Books You Can Borrow From Somebody;
  * Books That Everybody's Read So It's As If You Had Read Them, Too;
  * Books You've Been Planning to Read for Ages;
  * Books You've Been Hunting for Years Without Success;
  * Books Dealing With Something You're Working on at the Moment;
  * Books You Want to Own So They'll Be Handy Just in Case;
  * Books You Could Put Aside Maybe To Read This Summer;
  * Books You Need To Go With Other Books On Your Shelves;
  * Books That Fill You With Sudden, Inexplicable Curiosity, Not Easily Justified;
  * Books Read Long Ago Which It's Now Time To Re-read;
  * Books You've Always Pretended To Have Read And Now It's Time To Sit Down And Really Read Them;
  * New Books Whose Author Or Subject Appeals To You;
  * New Books By Authors Or On Subjects Not New (for you or in general);
  * New Books By Authors Or On Subjects Completely Unknown (at least to you)

by [[Italo Calvino]] - If on a Winter's Night a Traveler