Advertising Through Amazon is Working for Me!

I've been running adds for my Kindle published books through Amazon for over a year. Most of the time, my ACos (Advertising Cost of Sales) runs around 400%, but I set up some new adds at the beginning of this month, and they are doing really well. One of them is actually at 75%, another at 102%--which means they are actually profitable. People are seeing my adds, clicking on them, and buying my book!  I know that's how it's supposed to work, but it hasn't been working that way for me, until this new set of adds.  So what did I do differently this time? Good question! Let me see if I can explain!
First of all, I took advantage of all of the room I've been given within the add without repeating anything.  I didn't restate the title, as I have in the past. I didn't include information they can get from the title, the cover, or anything unimportant.  I tried to compliment the synopsis so that, once a potential reader clicks through, they can find out different information from the book blurb, not a repeat of what I already said.  I think this has helped!

My current add for Transformation

I'm also not running ads for the second and third book in my series. People are probably not going to buy those books until after they buy the first one, so I may as well sink my advertising money into that first book instead of the second and third.
The books that are doing the best have the most professional coves as well. They are the two that I paid the most for. Most of my books do have professionally designed covers, but when it comes to that initial image, you get what you paid for. Look at these three books. Can you tell me which cover I paid the most for?

The answer is Ghosts of Southampton. I paid $30 on Fiverr for the cover for Resurrection, and I did the cover for Doll Maker myself. Transformation is selling really well with these new ads, and I definitely think the professional cover is helping!
I've seen a huge boost to my sales this week, and even though I'm still not a "Best Seller," it's nice to see my books climbing the charts!  I'm having more luck running ads through Amazon Kindle than anywhere else I've ever tried!
Where do you like to advertise? What works for you?