First let's talk about how much it costs, because this stuff doesn't come cheap.
For £85 you can fund a shopping spree in Zara, forty-three bottles of Superdrug own brand shampoo or twice-daily Starbucks visits for a month.
But £85 will only buy you one small 30ml bottle of Sunday Riley's Luna Sleeping Night Oil.
But if you're willing (and able) to part with the cash, this stuff is the absolute bomb. How do I know? Because I started using it two months ago and my skin has never looked better.
I have what I would call a healthy cynicism about beauty products which cost more than my phone bill, so when a friend gave me a bottle of Luna Sleeping Night Oil I gave it a go without expecting the earth to move. The earth did not move, but I did wake up the next day and see a visible difference when I looked in the mirror. 'You might just be having a good skin day' said my husband nervously, always keen to discourage any beauty habits which look like they're going to become expensive.
The Luna Sleeping Night Oil comes in a small blue bottle with a glass pipette. The most noticeable thing is the oil's dark blue, ink-like colour and consistency. When I first rubbed it onto clean skin just before bed it gave my face a weird blueish tinge. But you'll be pleased to hear the Smurf look is only temporary, and I later learned that if you turn your face very blue it's a sign you're using too much of it.
The star ingredient of Sunday Riley's Luna Oil is the retinol (vitamin A), which has been hailed as a bit of a wonder-ingredient by beauty experts, helping reduce pore size, fine lines and plump the skin. As a teenager I was cheerfully informed by a beauty counter worker that I have 'oversized pores' on my face, particularly around my nose and forehead, so the big thing I noticed after using the Luna Oil for the first time was how much smaller my pores looked in the morning.
The oil also contains blue tansy, whose anti-inflammatory properties have made it this year's buzziest beauty ingredient, and it's also packed with those well known skin-goodies chamomile and avocado seed oil.
My husband's hopeful suggestion that I was just in a good skin phase lost its legs by week four, when my skin felt consistently smoother and glowier than I'd ever seen it, so much so that I started regularly going to work without any make-up on at all.
The other thing I've noticed from using it - which is better news for my husband - is how long the oil lasts. I've had the same bottle for two months and it's still a quarter full, even after I came back one Saturday night and managed to drunkenly spill a considerable amount of it on the bathroom counter.
And I'm not alone in my Sunday Riley fandom: Julianne Moore (who at 54 appears to be ageing backwards) and Stella McCartney apparently swear by the brand too, and when the Luna Sleeping Night Oil launched on Sephora back in March it sold out in minutes.
'Oh yes Sunday Riley is VERY good' said InStyle's beauty director Cassie when I mentioned my love of the product to her recently, 'you should also try her cleanser.'
This could all get pretty expensive. Sorry husband.
Sunday Riley's Luna Sleeping Night Oil, £85, is available from Cult Beauty