Even though the subtitle of the book is "How I Learned to Pay Attention, Master Myself, and Win", I didn't see much about any of these.

The book is more of a diary, with a lot of very superficially analyzed psychology theories.

Short summary: Maria, a Harvard alum and a writer for New Yorker, decides to write a book about poker and gives herself a year to master the game she knows nothing about. To do this, she approaches one of the top poker players, Erik Seidel, to be her mentor throughout this journey. He agrees and Maria goes on to win a few minor events and cash in a few major ones.

That's about it but that wouldn't make for an interesting story, would it?

Maria tries to squeeze more meaning from what she's done than there actually is to it. Citing the title of her book: there's not much about "how I learned to pay attention", or "how I mastered myself" or "how to win". The title was probably a well-researched and tested version that her publisher thought would sell best.

There's an interesting outcome that I took from the book, that wasn't even mentioned in it:

When you have a safety net and don't have to worry about the finances, and can afford to dedicate a year of your life to whatever you want, and give 100% of your time to it, with deliberate practice, being coached by one of the top names in the given industry, you can go from zero to a semi-pro level and see meaningful results.

I guess the publisher decided it would be too long for the book's subtitle.

If you don't focus on the original subtitle and more on the one above, the book and the story will be much more interesting.