This detail page shows several photos of the book to show what a first edition looks like.  The images are original photos taken of my personal copy of the first edition book. 

Three Doors to Death (1950):

• The dustjacket has some unique features:
• The front flap is red and has the price ($2.50) at the top and "The Viking Press New York" at the bottom.  The book club edition has white flaps.
• The back flap is red and has two lines about Viking Press above "Printed in USA". The book club edition has white flaps.
• The back of the dustjacket has "The Viking Press New York" at the bottom, which is not present on the book club edition.
• The title page on the first edition has all black text, while the book club edition the keys and "A Nero Wolfe Threesome" are in red.
• The copyright page has the colophon and "Printed in the USA by Vail-Ballou Printing Company" on it. 
• The first edition book cover is green cloth with blue lettering, while it is smoother and blue on the book club edition.
• I have included an animated GIF file that compares many of the relevant points for a clearer understanding.
• The first edition measures 1.07" x 5.6" x 8.25"
• The book club edition measures .9" x 5.7" x 8.5"
• I also have a video on our YouTube channel you can watch here