As the name indicates, the Obituary Cocktail is not a tame drink and it is the concentration of absinthe (which equals dry vermouth here) that is likely the source of the warning. That aside, it is a stellar drink that retains the opalescence of the traditional absinthe drink, simply bringing it into the classic Gin Martini mix.
If you are new to or rediscovering absinthe, this is the cocktail to try because it makes for a very fine tasting experience. Remember, don't skimp on the quality of the gin here either, because cheap gin equals a cheap (tasting) drink.
If you like or if they are simply more accessible, any absinthe substitute (such as Pernod) will do here.