With any book, I think you have to REALLY make a connection with the book to benefit greatly. No matter what book you've read, it has become part of you — even if it's a tiny amount.

You have to study the book: take notes as you read it, practise what you've learned, read it again and read your notes. That's what I started doing recently.

For books I want to REALLY study, I put a "reread" label on it. On my first read through, I take notes (anything that seems significant) on an A4 pad labelled "reading study copy" and read over the notes ive just written after that reading session. When you finally reach the end of the book, read all the notes you've written, and occasionally read over them to remember. Then add "1" on the bottom of your label to signify your first read through. Then read through again at some point, and repeat the process.

My personal self-development/self-help books that I found FANTASTIC!:

Overcoming Social Anxiety & Shyness by Gillian Butler.

The Chimp Paradox by Professor Steven Peters.

Can't Hurt Me by David Goggins.

Surrounded by Idiots by Thomas Erikson.