The actor is putting pen to paper to memorialise his Star Trek co-star in a book called Leonard: A 50 Year Friendship, and he has been interviewing friends and colleagues from Nimoy's past to gather material for the tome, reports

The book, which will recount the pair's longtime friendship, is reportedly slated for release in 2016 by the St. Martin's Press publishing house.

Nimoy died in February (15) at the age of 83.