The secret method of chartreuse's preparation is held by three monks bound by a vow of silence, and I've heard a further rumor that no one of these three Carthusians ever knows the entire recipe or list of ingredients, but only a jig-saw piece portion, and thus they are never allowed to travel together in the same automobile. I have no idea if this is true, but it certainly adds to the drink's mysterious allure.
I introduced this complex, enthralling liquor to one friend who immediately commented that it tasted like drinking a Christmas tree. At 110 proof it certain has over 25% more alcohol content than your average hard booze (80 proof). That said, though, if drank wisely and solely through an evening, it can produce one of the most pleasant, coherent, transcendental drunks possible. By dawn you'll have talked earnestly, animatedly, but never disputatiously, about everything under the stars, from Nero to neutrinos.
Later, once you hit the sack, you may also find as I did that charteuse affects your dreams, opening gates on dreamscapes that normally aren't available to you. This isn't always pleasant, since some of the new characters and locales can be frightening in their novelty, or just plain frightening. But if you want to shakeup your nocturnal wanderings, chartruese can help do the trick.
Four of us rang in the year 2000 drinking green chartreuse on the edge of the continent in a Jersey Shore beach gazebo; and under the dark roiling sky, a stone's throw from the dark roiling ocean, we understood how silly humankind's reckoning of time really is.