(I buy a mix of ebooks and hard copy books, but a screenshot of Calibre isn't as good!)
Links are to Amazon UK (other bookstores are available), and they are not affiliate links.
Here are some of my favourites:
Getting Things Done: The Art of Stress-free Productivity: probably one of those "Marmite" books, but the GTD principles really work for me, and help me manage my time and increase my productivity / efficiency. My key efficiency tip is that you don't need to read most of this book — the flowchart will tell you pretty much all you need to know to get started.
Presenting / speaking
The Presentation Secrets of Steve Jobs: How to Be Insanely Great in Front of Any Audience: hyperbolic title, but I learned a lot from this, and it's certainly influenced how I present.
Zen and the Art of Stand-Up Comedy: I'd like to think that my presentations are entertaining as well as informative, and the principles from this helped me develop that.
Confessions of a Public Speaker Paperback: useful in terms of planning, dealing with things going wrong, and generally about being a compelling speaker.
Negotiating (including price!) / deescalating / conflict resolution
Getting to Yes: Negotiating Agreement Without Giving: I still find some of the principles for negotiating in here useful, although I have tempered them with some of the suggestions from "Never Split The Difference".
Never Split the Difference: Negotiating as if Your Life Depended on It: a different approach to "Getting To Yes", with clear, practical guidance (and only a couple of hours to read it, if you skip over some of the numerous, lengthy, case studies) .
Crucial Conversations Tools for Talking When Stakes Are High: another book about talking, and getting people to open up, to assist in avoiding and resolving conflict.
Advocacy / influencing
The Devil's Advocate: useful for improving both written and oral advocacy and influencing, which accounts for a large amount of what I do for clients (even though we don't do litigation).
A Manual of Style for Contract Drafting: I'm halfway through Ken's live virtual "Masterclass" course, and I'm so delighted I've finally found the time to do it. The accompanying book is great, but forcing myself to look at how to improve the way I write agreements is even better.
Typography for Lawyers: Essential Tools for Polished & Persuasive Documents: yes, really. Typography for Lawyers. Lots of useful tips to make your documents look better, which makes them easier to understand/
True Worth: How To Charge What You're Worth And Get It: this is a short book, but it is worth a quick flick. I still struggle with pricing, and this helped me think about describing the true value to a prospective client of what they'd get from engaging me.