"Tiny Habits" by Dr. BJ Fogg, a research associate at Stanford, is my preferred book (though my view is more boring: I think "Atomic Habits," "The Power of Habit," and "Tiny Habits" are all worth a glance-through).

From my personal experience, I remembered the most from this book years later, in contrast to the other two. Specifically, I still use the idea of "prompts" for behaviour change. I remembered how it's typically not a good idea to use time as a prompt to do something (e.g. this is not effective: "At 8 pm every day, I will go outside for a jog"), but instead to use a prompt that's easy to notice (e.g. this is more effective: "After dinner every day, I will go outside for a jog").

I also really appreciated the idea of avoiding personally blaming yourself or others for unwanted behaviour, and looking at systems change first. I still remember the author's anecdote about solving a conflict with a roommate who complained about the bathroom floor being wet too often: instead of focusing on guilting the person, the systematic change was simply to put a bathroom towel on the floor to make it easier to dry the floor. Similarly, I've been able to keep my own bathroom cleaner by putting cleaning tools in easier reach.

Lastly, I appreciated the appendix that contains book summary charts, mnemonics (e.g. a habit can be thought of as "ABC": an anchor/prompt, a behaviour, and a celebration), and suggested habits (especially positive habits that help with tending to interpersonal relationships).

I still remember all of this years later, so in my personal experience, this book had the greatest impact on me.

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For "The Power of Habit" by Charles Duhigg, it's a bit harder to skim as it lacks the graphs and summaries from "Tiny Habits." However, the ideas are mostly the same. For example, this book focuses on triggering behaviour with "cues,” which are equivalent to "prompts" in "Tiny Habits.”

The idea of “keystone habits” also stood out as more emphasized to me in this book, where certain habits can have the most impact in contrast to others.

I suspect this book was popular because you might feel smarter from reading it, as it explores case studies about corporations and US military training, but it’s a bit harder to skim to refresh, due to lacking the graphs and summaries of the other two books.

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For "Atomic Habits" by James Clear, I respect the book for what it is. It's engaging for most people to read, popular, and it makes the ideas easy to understand for lots of people. I prefer "Tiny Habits" more, but I respect “Atomic Habits” for making the ideas accessible to a larger audience.

I actually found it fairly similar to Tiny Habits: it also has diagrams, and it also has mnemonics (e.g. a habit as a Cue-Craving-Response-Reward). The author also talks about making positive habits easier to do in simple ways, similar to the “Tiny Habits” author.

I believe the biggest difference between the two was that "Atomic Habits" focused more on motivating behaviour change by focusing on a want to change your identity (e.g. by reminding yourself that a person you would want to become would practice different habits). This might be a source of criticism about the book, as the advice is less practical in contrast to the other ideas, though it has some plausibility (e.g. in my personal experience, reminders that one is a professional have been effective at changing behaviour).

Upon a skim now, I do remember having the feeling that the ideas of “Atomic Habits” were similar to those of “Tiny Habits,” but I preferred the “Tiny Habits” appendix more, and I also had a personal preference for the writing style of the book by Fogg.

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To summarize this whole comment, I believe all three are worth at least a skim, though I like “Tiny Habits” the most for the writing style and provided graphs and mnemonics. But you can’t go wrong if you’re interested in habit change with any of them, as they overlap a lot and roughly cover the same ideas for behaviour change.