I found out about this product on Hot and Flashy, the blog by Angie which several of us follow. A link on her site will give you a $5 off discount, and I believe a bottle is about $25 so it's a good deal. I've been using it for a month and like it, though of course I can't make any claims for the effectiveness yet. Angie has a video or 2 about this and why she uses it, citing a recent study showing that Vitamin C applied to the skin under sunscreen makes the sunscreen 3 or 4 times more effective (please read Hot and Flashy to get the exact details as I can't remember). I use it on the backs of my hands, face and neck once a day. It's an oil but pretty quickly absorbed, doesn't smell, sting or stain clothing.
I believe it is identical or nearly so to the Skinceuticals Vitamin C + Ferulic which sells for something like $162!!
This is a case where I'm happy to use an affiliate link provided by a beauty blogger.