Best Edition 
When two or more editions of the same version of a work have been published, 
  the one of the highest quality is generally considered to be the best edition. 
  In judging quality, the Library of Congress will adhere to the criteria set 
  forth below in all but exceptional circumstances. 
The criteria to be applied in determining the best edition are listed below 
  in descending order of importance. In deciding between two editions, a criterion-by-criterion 
  comparison should be made. 
The edition that first fails to satisfy a criterion is to be considered of 
  inferior quality and will not be an acceptable deposit. Example: If a comparison 
  is made between two hardbound editions of a book, one a trade edition printed 
  on acid-free paper, and the other a specially bound edition printed on average 
  paper, the former will be the best edition because the type of paper is a more 
  important criterion than the binding.
  -  Paper, Binding, and Packaging:  
    
      -  Archival-quality rather than less-permanent paper
-  Hard cover rather than soft cover
- Library binding rather than commercial binding
-  Trade edition rather than book club edition
- Sewn rather than glue-only binding
-  Sewn or glued rather than stapled or spiral-bound
- Stapled rather than spiral-bound or plastic-bound
-  Bound rather than looseleaf, except when future looseleaf insertions 
        are to be issued. In the case of looseleaf materials, this includes the 
        submission of all binders and indexes when they are part of the unit as 
        published and offered for sale or distribution. Additionally, the regular 
        and timely receipt of all appropriate looseleaf updates, supplements, 
        and releases including supplemental binders issued to handle these expanded 
        versions, is part of the requirement to maintain these publications properly 
      
-  Slip-cased rather than nonslip-cased
-  With protective folders rather than without (for broadsides)
-  Rolled rather than folded (for broadsides)
-  With protective coatings rather than without (except broadsides, which 
        should not be coated)
  
  
   
-  Rarity: 
    
      -  Special limited edition having the greatest number of special features
-  Other limited edition rather than trade edition
-  Special binding rather than trade binding
  
   
-   Illustrations: 
    
      -  Illustrated rather than unillustrated
-  Illustrations in color rather than black and white
  
   
-  Special Features: 
    
      -  With thumb notches or index tabs rather than without
-  With aids to use such as overlays and magnifiers rather than without
 
 
  
-  Size: 
    
      -  Larger rather than smaller sizes. (Except that largetype editions for 
        the partially-sighted are not required in place of editions employing 
        type of more conventional size.)