Full of math, you can read about it here Edward Robertson.
There is also what James Lewis experienced here James Lewis.
I'm summarize what they both said. It ain't working anymore.
Giving away books used to work but it doesn't really impact sales now. What did I say months ago? The GIMME CAP STRATEGY. Only give away stuff that isn't valuable to you. Like the buttercup book. If you think that momentary burst of visibility will help you, then go with Select. It's a gamble. Repeat. It's a gamble.
If you just want people to see what you do, Select is great. Ish. It's a good place to experiment or do something different just for your satisfaction.
I'm sure, no really I am, that it is super for some people and they'll tout its glory. Those writers are now outliers. You can't make a gameplan based on outliers. You're already an outlier and you have to come up with your plan specific to your work. Note that I didn't say book. A book is too small of a concept at this juncture in publishing. You have to think big/long-haul/career.
I don't know what else to say. Write something super commercial. People will find you. Or write what you want to write but tradpub was a roadblock and hope people find you.