(Find me at 50 Watts Books.)

A big thank you to VonMurr for sending the first ten covers in this post. They come from his personal collection. The others were found on online Polish bookstores.

Zygmunt Zeydler-Zborowski, Czerwona nitka (Red thread), Seria Z Jamnikiem, Czytelnik Warsaw 1972, 1st edition
Cover Przemysław Bytoński

Jerzy Edigey, Sprawa Niteckiego (Nitecki's affair), Seria Z Jamnikiem, Czytelnik Warsaw 1966, 1st edition
Cover Jan S. Miklaszewski

Zygmunt Zeydler-Zborowski, Pieczeń sarnia (Deer roast). Seria Z Jamnikiem, Czytelnik Warsaw 1973, 1st edition

Jerzy Edigey, Walizka z milionami (Suitcase with millions), Seria Z Jamnikiem, Czytelnik Warsaw 1975, 1st edition
Cover Jolanta Musiałowicz-Jankowska

Jerzy Edigey, Baba Jaga gubi trop (The witch looses the trial), Seria Z Jamnikiem, Czytelnik Warsaw 1967, 1st edition

Zygmunt Zeydler-Zborowski, W kręgu podejrzenia (In the circle of suspiction), Seria Z Jamnikiem, Czytelnik Warsaw 1975, 1st edition
Cover Marian jankowski

Jerzy Edigey, Zbrodnia w południe (Crime at midday), Klub srebrnego klucza, Iskry Warsaw 1970, 1st edition
Cover Mieczysłw Kowalczyk

Zygmunt Zeydler-Zborowski, Brat Mikołaja (Nicolas's brother), Klub srebrnego klucza
Iskry Warsaw 1974, 1st edition
Cover Mieczysław Kowalczyk

Zygmunt Zeydler-Zborowski, Koty Leokadii Kościelnej (Leokadia Kościelnacats), Klub srebrnego klucza, Iskry Warsaw 1975, 1st edition
Cover Mieczysław Kowalczyk

Jerzy Edigey, Strzały na rozstajnych drogach (Shots at cross roads), Seria Z Jamnikiem, Czytelnik Warsaw 1975, 1st edition
Cover Przemysław Bytoński

March 2011 update: If you at all like these you owe it to yourself to buy the book 1000 Polish Book Covers (it probably won't be in print forever).