Lucy and Ricky argue over a murder mystery novel in the I Love Lucy episode The Black Eye. I finally identified the book after numerous screen captures and zooming in Photoshop to bring you the ID of the book. The title is The D.A. Takes a Chance by Erle Stanley Gardner who is also the author of the famous Perry Mason novels.
Following are some pictures of early editions. The hard cover of Lucy’s book looks like the 1st edition of 1948. I see several versions of the book on Amazon and eBay so there still time to get yourself a scary thrillerfor those dark winter evenings.

See it on eBay

Reference:

• http://www.amazon.com/D-Takes-Chance/dp/B002ODCC20
• https://en.wikipedia.org/wiki/Erle_Stanley_Gardner