Many philatelic reference books are collectible in their own right since many renowned hobby experts are now out of print. Most are valued for their collectability based on condition, rarity, and to some extent their use as a reference. Condition is the key and is highly subjective, so study the images, read the content, ask questions, and work with a reliable collector-dealer to get what you want.
MEMBER:
Olympia Philatelic Society
American Philatelic Society
U.S. Philatelic Classics Society