I read The Slight Edge a few months ago.
Since then, it's been the book I recommend most often to most people. (I don't make book recommendations willy-nilly, but if something seems relevant to what the person I'm speaking to is experiencing/thinking about, I make a recommendation.)
I joyfully recommend other books about career advice, money management, exercise, and I love fiction, so I've always got a bunch of those ready to recommend too, but usually The Slight Edge is the most appropriate recommendation.
I wish I could recommend the Kindle version of the book, but... I can't. :(
Jeff Olson wrote the first version maybe ten years ago. It was a massive success. So, recently, he wrote an "updated" version, that basically spends half the book explaining how good the ideas in the first version are, and all the spin-off books, conferences, etc that have come from it.
The content of the most recent version is still good, it's just filled with tons of fluff that doesn't need to be there.
Even the 2nd version has an 88% rate of five stars, out of about 1000 reviews, so not too shabby, but feel free, if you read it, to skip the bits that you don't want to read.
Here's the premise of the book:
Small actions, taken every day, compound. They compound in a way that hurts you, or in a way that helps you. Progress may seem nonexistent, but take joy in the small beneficial "slight edge" actions you can take, and over time, you'll have something great. Conversely, if you take the slightly easier option of many small harmful (or neutral) decisions every day, over time these compound against you and your health, relationships, finances, etc.
Go read the book. The original edition costs $7 + shipping via Amazon (I don't do affiliate links, by the way.) and you can read it over the next month. That's about 10 minutes of reading a day.
I referenced this book when I wrote that "Everything I do and think I've read in a book", and how the mentality outlined in this book trickle down through every part of your life, whether you are aware of it or not.