Rather than by typical self-help authors
written by scientists or people who are experts in their subject
I tend to prefer books written by scientists or people who are experts in their subject rather than by typical self-help authors. I find that when someone knowledgeable helps me understand how something works, it's much easier to figure out how to apply this knowledge to life.
Books I liked:
How We Learn by Stanislas Dehaene. Made me tweak and streamline my learning habits. (There is another older book of the same name but by a different author which I never read).
How to Take Smart Notes by Soenke Ahrens. A very good practical guide on note-taking when reading and studying. One slight drawback is that the author tends to recommend only one app for notetaking but this can be safely ignored.
Why We Sleep by Mathew Walker. Helped me develop better sleep habits.
Never Split the Difference by Chris Voss. A really good book on negotiation.
How to Speak Well by Patrick Wilson and Confessions of a Public Speaker by Scott Berkun. Both have many useful tips for public speaking.