I'll go with:

The Brain That Changes Itself,

by Norman Doidge

The book is trying to summarize the (at the time) state of neuro-science.
It's separated into different anecdotes.
Considering the magnitude of knowledge it includes, it's an easy read.
It's mainly about the concept of 'neuro plasticity'.

The book changed my life in many ways...

At the time, I was chilling in a hippy village, for almost 9 weeks.
I spent my days sitting in the community tent, talking to people, playing chess, whittling and reading.
I never planned on staying there for a long time... It just happened.
I never planned on reading that book, I just stumbled upon it, in a 'free stuff' shelf.

I was in the perfect setting to let the contents 'sink in' and immediately apply some of the lessons it contained for me;
I had a lot of time to reflect on my life and all sorts of things, and this book gave me new tools to analyze behaviors and to understand how learning works in general.

I have since used this new set of tools to learn new things, condition myself differently, help others progress on their journey to improve themselves.

It has the power to change the way you see yourself and others.
One main message (though never explicitly stated within): You are not your thoughts.
You can change your thoughts, your patterns, your viewpoint.
It really helped me in many ways and still does.

EDIT: my favorite quote from the book:
"If you don't use it, you'll lose it"
It explains a critical concept of how neuronal networks (in the brain) work, but also (more broadly speaking) applies to skills and other things you have learned.

That was 244 words, but I feel like, I should do it more justice by dedicating a blog post to it. The above was off the cuff and I didn't really try to re-read it.
I think I might have written a post about it in the past, but I'd have to search...

I tried hosting a similar contest, with higher prize money even, and got very few participants. It can be frustrating.

I recommend you include tagging other people as condition.
Then again, even though my contest had only 1 single rule, people still disqualified themselves.
It all goes back to people not reading... but that is another debate...

Thanks for hosting the contest, I hope it goes well.
If you need a script (bot) to handle the replies, don't hesitate to contact me. I make tools for Hive.
Followed your account for good measure.