Sorry, you asked about Curl Keeper too....I use this most days after my leave-in and sealer, as I live in Florida where there are high dews most of the year and I find it definitely helps the frizzies! For me, though, it has no hold and so I don't use it as a stand alone styler; always mousse, gel or jelly on top.
However, since you have fine hair, it may work for you especially if you like a soft look with no crunch. I would say this is a definite purchase, at least to try it. You can use a lot of it and it doesn't hurt. In fact, the only issue I find is if I don't use enough.
2C/ Coarse/ Normal porosity/ SW Florida/ Transitioning to gray
Cleanse: CJ Daily Fix, JC Cleansing Cream, TJ Tea Tree Condish
Condish: JC Too Shea, CJ Curl Rehab (both as RO & LI)
Stylers: UFD CM, CJ PP, JC Spiralicious, Darcy's Cream Gel & Cocoa bean whip