I've just got this game. The card "Book of Medicine" reads: "At the end of each of your turns..." so shouldn't the card be listed as Remains In Play?
Since the book is an Item, like a gun or jacket, it remains on the player until the player loses it.
'Remains in play' concept is geared to events that alter game play, usually Mystery cards Like "Fog" but some Events are remain in play such as "Strength of XXX" meaning the player permanently increases their attribute.
OK, thanks for the clarification.