This is for one  Nancy Drew Book-pick one for one price ,28, 29, 30 and 31 by Carolyn Keene. All have the blue end pages. Titles and brief description follows. Any questions, please ask, and thanks for looking!The price is for one book just let me know which one you want and I can then remove it from the listing.
The Clue of the Black Keys - 1951-inscription inside, small bit of wear to bottom of spine.

The Mystery at the Ski Jump - 1952-small bit of wear to bottom and top of spine
The Clue of the Velvet Mask- 1953-small bit of wear to bottom and top of spine
The Ringmaster's Secret- 1953 -again some minimal wear to top and bottom of spine