The Most Highly Recommended: 

  The Postcard Price Guide by J.L. Marshburn. Even if you just pick up a card here and there, this reference guide will give you an idea of what to look for in the way of rarities so you can keep an eye out for bargains. It’s also lots of fun to page through just to look at the photos, and offers a good historical perspective as well.
 

Highly Recommended:

• Picture Postcards in the United States 1893-1918  by Dorothy Ryan 
• The Artist-Signed Postcard Price Guide- A Comprehensive Reference
  by J. L. Mashburn
  
•  Postcard Companion: The Collector’s Reference by Jack.H. Smith
• The Encyclopedia of Antique Postcards/Price Guide (Wallace-Homestead Price Guide) by Susan Brown Nicholson
• Standard postcard catalog;: A price guide for postcard collectors, by James Lewis Lowe
• The Collector’s Guide to Postcards by Jane Wood
  

Recommended:

• Fantasy Postcards With Price Guide, A Comprehensive Reference by J.L.Mashburn
  
• Vintage Postcards for the Holidays- Identification & Value Guide
  by Robert Reed, Claudette Reed
  
• The American Postcard Guide to Tuck by Sally Carver
• Postmarked Yesteryear- Art of the Holiday Postcard  by Pamela E. Apkarian-Russell
  

Tags: books, collecting, postcard, price guide, reference