British Collins Tall Pictorial Cover Editions:
Three Investigators #1: The Secret of Terror Castle Very Good Condition 1969 Printing $ 25
Three Investigators #2: The Mystery of the Stuttering Parrot Very Fine Condition 1971 Edition $ 35

British Collins Short Pictorial Cover Editions:
Three Investigators #2: The Mystery of the Stuttering Parrot Very Good Condition (18) $ 25
Three Investigators #4: The Mystery of the Green Ghost Very Good Condition (6) $ 25
Three Investigators #4: The Mystery of the Green Ghost Very Fine Condition (6) $ 35
Three Investigators #4: The Mystery of the Green Ghost Very Good Condition (12) $ 25
Three Investigators #4: The Mystery of the Green Ghost Very Fine Condition (18) $ 35
Three Investigators #7: The Mystery of the Fiery Eye Very Good Condition (16) $ 25
Three Investigators #11: The Mystery of the Talking Skull Very Good Condition (12) $ 25
Three Investigators #11: The Mystery of the Talking Skull Very Good Condition (16) w/Front Endpaper Damaged $ 25
Three Investigators #11: The Mystery of the Talking Skull Very Good Condition (16) $ 25
Three Investigators #17: The Mystery of the Singing Serpent Fair-Good Condition (18) $ 15

Random House "Silhouette-Spine" Paperback Editions w/Marchesi Artwork:
Three Investigators #7: The Mystery of the Fiery Eye Very Good Condition 2nd Paperback Printing $ 10
Three Investigators #7: The Mystery of the Fiery Eye Very Good Condition 7th Paperback Printing $ 10
Three Investigators #8: The Mystery of the Silver Spider Good Condition 1st Printing $ 8
Three Investigators #8: The Mystery of the Silver Spider Very Good Condition 1st Printing $ 10
Three Investigators #8: The Mystery of the Silver Spider Very Good Condition 7th Printing $ 8
Three Investigators #9: The Mystery of the Screaming Clock Fair-Good Condition 1st Printing w/Waterstain $ 5
Three Investigators #10: The Mystery of the Moaning Cave Good Condition 8th Paperback Printing $ 6
Three Investigators #11: The Mystery of the Talking Skull Very Good Condition 7th Printing $ 10
Three Investigators #12: The Mystery of the Laughing Shadow Very Good Condition 1st Printing $ 12
Three Investigators #12: The Mystery of the Laughing Shadow Fine Condition 3rd Printing $ 15
Three Investigators #12: The Mystery of the Laughing Shadow Good Condition 7th Printing $ 10
Three Investigators #12: The Mystery of the Laughing Shadow Very Good-Fine Condition 9th Printing w/Slight Waterstain $ 10
Three Investigators #15: The Mystery of the Flaming Footprints Very Good-FIne Condition 7th Printing $ 15
Three Investigators #18: The Mystery of the Shrinking House Good Condition 1st Printing $ 8
Three Investigators #18: The Mystery of the Shrinking House Fair-Good Condition 4th Printing $ 5
Three Investigators #18: The Mystery of the Shrinking House Very Good-Fine Condition 9th Printing $ 10
Three Investigators #26: The Mystery of the Headless Horse Very Good-Fine Condition 2nd Printing $ 20
Three Investigators #27: The Mystery of the Magic Circle Good Condition 3rd Paperback Printing $ 10
Three Investigators #27: The Mystery of the Magic Circle Very Good-Fine Condition 3rd Paperback Printing $ 10
Three Investigators #30: The Secret of Shark Reef Very Good Condition 3rd Printing $ 20

Random House "Key Hole" Paperback Editions w/Adragna Artwork:
Three Investigators #1: The Secret of Terror Castle Good Condition 6th Printing $ 10
Three Investigators #4: The Mystery of the Green Ghost Good Condition 3rd Printing $ 8
Three Investigators #7: The Mystery of the Fiery Eye Very Good-Fine Condition 1st Revised Printing $ 15
Three Investigators #8: The Mystery of the Silver Spider Very Good Condition 1985 1st Revised Printing $ 15
Three Investigators #11: The Mystery of the Talking Skull Very Good Condition 5th Printing $ 12
Three Investigators #15: The Mystery of the Flaming Footprints Very Good Condition 4th Printing $ 15
Three Investigators #24: The Mystery of the Death Trap Mine Very Good-Fine Condition 4th Printing $ 15
Three Investigators #26: The Mystery of the Headless Horse Very Good Condition 1st Printing $ 20
Three Investigators #31: The Mystery of the Scar-Faced Beggar Very Fine Condition 5th Printing $ 25
Three Investigators #31: The Mystery of the Scar-Faced Beggar Very Good-Fine Condition 6th Printing $ 20
Three Investigators #32: The Mystery of the Blazing Cliffs Very Good Condition 3rd Printing $ 15
Three Investigators #32: The Mystery of the Blazing Cliffs Fine Condition 5th Printing $ 20
Three Investigators #32: The Mystery of the Blazing Cliffs Very Good-Fine Condition 6th Printing $ 20
Three Investigators #32: The Mystery of the Blazing Cliffs Very Fine Condition 6th Printing $ 25
Three Investigators #33: The Mystery of the Purple Pirate Very Good-Fine Condition 3rd Printing $ 20 (2 Copies Available)
Three Investigators #35: The Mystery of the Kidnapped Whale Fine Condition 1st Printing $ 30
Three Investigators #35: The Mystery of the Kidnapped Whale Fine Condition 5th Printing $ 25
Three Investigators #36: The Mystery of the Missing Mermaid Very Good-Fine Condition 2nd Printing $ 30 (2 Copies Available)
Three Investigators #37: The Mystery of the Two-Toed Pigeon Fine Condition 1st Printing $ 35 (2 Copies Available)
Three Investigators #38: The Mystery of the Smashing Glass Fine Condition 1st Printing $ 35
Three Investigators #39: The Mystery of the Trail of Terror Fine Condition 1st Printing $ 35
Three Investigators #40: The Mystery of the Rogues' Reunion Fine Condition 1st Printing $ 45
Three Investigators #40: The Mystery of the Rogues' Reunion Fine Condition 1st Printing $ 45
Three Investigators #41: The Mystery of the Creep-Show Crooks Very Good-Fine Condition 1st Printing $ 45
Three Investigators #41: The Mystery of the Creep-Show Crooks Fine Condition 2nd Printing $ 40
Three Investigators #42: The Mystery of Wreckers' Rock Very Good Condition 1st Printing $ 40
Three Investigators #42: The Mystery of Wreckers' Rock Very Good-Fine Condition 1st Printing $ 45
Three Investigators #42: The Mystery of Wreckers' Rock Very Fine Condition 1st Printing $ 55

Scholastic Paperback Editions:
Three Investigators #4: The Mystery of the Green Ghost Very Good Condition w/Liese Artwork $ 10
Three Investigators #8: The Mystery of the Silver Spider Very Good Condition $ 6
Three Investigators #10: The Mystery of the Moaning Cave Fine Condition $ 8
Three Investigators #11: The Mystery of the Talking Skull Fine Condition $ 8 (2 Copies Available)
Three Investigators #15: The Mystery of the Flaming Footprints Very Good Condition w/Charles Liese Artwork $ 12
Three Investigators #19: The Secret of Phantom Lake Fine Condition $ 10
Three Investigators #20: The Mystery on Monster Mountain Fine Condition $ 10
Three Investigators #21: The Secret of the Haunted Mirror Very Good Condition $ 8
Three Investigators #30: The Secret of Shark Reef Very Good Condition w/Liese Artwork $ 15

Alfred A. Knopf Bullseye Paperback Editions:
Three Investigators #2: The Mystery of the Stuttering Parrot Fair Condition 1st Printing Former Library Copy $ 2
Three Investigators #10: The Mystery of the Moaning Cave Good-Very Good Condition 1st Printing $ 5
Three Investigators #11: The Mystery of the Talking Skull Very Good-Fine Condition 1st Printing $ 8
Three Investigators #11: The Mystery of the Talking Skull Fine Condition 1st Printing $ 10
Three Investigators #21: The Secret of the Haunted Mirror Good Condition 1st Printing $ 5
Three Investigators #26: Mystery of the Headless Horse Very Good-Fine Condition 1st Printing $ 8
Three Investigators #26: Mystery of the Headless Horse Very Fine Condition 1st Printing $ 10 (6 Copies Available)
Three Investigators #32: The Mystery of the Blazing Cliffs Good Condition 1st Printing $ 5
Three Investigators #32: The Mystery of the Blazing Cliffs Very Fine Condition 1st Printing $ 10 (3 Copies Available)
Three Investigators #33: The Mystery of the Purple Pirate Very Good Condition 1st Printing 1991 $ 15

Random House Paperback Editions w/Dodge Cover Art:
Three Investigators #8: The Mystery of the Silver Spider Fair-Good Condition 6th Printing Former Library Copy $ 2
Three Investigators #9: The Mystery of the Screaming Clock Fair-Good Condition 11th Printing $ 2
Three Investigators #9: The Mystery of the Screaming Clock Very Fine Condition 11th Printing $ 12

British Armada Paperback Editions:
Three Investigators #1: The Secret of Terror Castle Good-Very Good Condition 1978 Printing $ 12
Three Investigators #2: The Mystery of the Stuttering Parrot Very Good Condition 1978 Printing $ 20
Three Investigators #3: The Mystery of the Whispering Mummy Very Good Condition 1971 Printing $ 15 View
Three Investigators #5: The Mystery of the Vanishing Treasure Very Good Condition 1978 Printing $ 15
Three Investigators #6: The Secret of Skeleton Island Very Good Condition 1978 Printing $ 15 View
Three Investigators #8: The Mystery of the Silver Spider Very Good Condition 1977 Printing $ 15 View
Three Investigators #9: The Mystery of the Screaming Clock Very Good Condition 1979 Printing $ 15
Three Investigators #21: The Secret of the Haunted Mirror Good Condition 1984 Printing Former Library Copy $ 10 View
Three Investigators #24: The Mystery of the Death Trap Mine Good Condition 1980 Printing $ 12
Three Investigators #29: The Mystery of the Sinister Scarecrow Very Good Condition 1989 Printing $ 20
Three Investigators #31: The Mystery of the Scar-Faced Beggar Good Condition Former Library Copy 1990's Printing $ 10 View
Three Investigators #39: The Mystery of the Trail of Terror Good Condition Former Library Copy 1993 Printing $ 10 View

Random House Find Your Fate Mystery Series Paperback Editions:
Three Investigators: The Case of the Weeping Coffin Fine Condition 1st Printing $ 35