Around 1979 or 1980 I received for my birthday a mystery books of sorts. It consisted of a thick bundle of documents related to a murder--letters from the victim and various suspects, newspaper clippings, diagrams of the house, and so on. It even had a small envelope with samples of the poison pills used to kill the victim, if I remember correctly. The solution to the crime was in a sealed envelope. The publishing company released several different versions, and mine had (again, if I remember correctly) a 1920s setting--very Agatha Christie in tone. I have been driving myself crazy trying to remember the name of the book, and I think it is something like The Bancroft Papers or The Bancroft Murder. Does this ring a bell for anyone?