NEW YORK — Accused CEO killer Luigi Mangione turned 27 last month, marking the occasion with a list of “27 Things I’m Grateful For” that he sent to various people who have been writing to him in jail and that is now circulating online.

Mangione is receiving so many letters – his attorneys said between 10 and 115 per day while in federal custody – that he wrote it is “creating a bizarre and disorienting Groundhog Day scenario where every day is both Christmas and my May 6th birthday.”

The suspected killer said he has received letters from more than 40 countries and “countless books,” including Ayn Rand’s “Anthem” and Ray Bradbury’s “Fahrenheit 451,” cluttering the “birdcage” he shares with his cellmate, identified as “J.”

Mangione has pleaded not guilty to state and federal charges stemming from the assassination-style shooting death of United Healthcare chief executive Brian Thompson. His next court appearance is scheduled for June 26, at which Judge Gregory Carro could set a trial date.

“If ever there were an open and shut case pointing to defendant’s guilty, this case is that case. Simply put, one would be hard pressed to find a case with such overwhelming evidence of guilt as to the identity of the murderer and the premeditated nature of the assassination,” Joel Seidemann, an assistant district attorney in Manhattan, wrote in a recent court filing. “While this is of no solace to Mr. Thompson, his family or his friends, the assassination was not personal to Mr. Thompson but rather a necessary part of defendant’s evil plan to usher revolutionary changes to the delivery of healthcare in the United States through the barrel of a gun.”

Mangione has sought to dismiss or delay the state case to concentrate on the federal case, which could yield the death penalty.