A lot of sales books teach Jedi mind tricks and "tricks to close" and crap like that. This is much more practical. It walks you through a customer's buying process and shows how you can map that to your sales process. I find that making a better connection with my clients comes from putting their best interest first and being a good person. No need for psychology or tricks. Once you understand the buying process, and you understand the products/services you're selling, you're good to go.
I came from a technical background as well and this was the only book that really explained the process to me without a bunch of "closing tricks" or other gimmicky sales tactics.
For marketing, I recommend Traction by the founders of Duck Duck Go. It gives a practical guide to tons of different marketing channels and when each one is appropriate https://www.amazon.com/Traction-Startup-Achieve-Explosive-Cu...
For sales, I recommend How You Make the Sale. It's a general sales book no matter if you're selling software, services, or physical goods and it does a great job of walking you through the sales process and where it overlaps with the buying process. It also helps reframe a lot of the "scary" parts of sales like objections as "requests for more information". Highly recommend for technical people who are new to sales https://www.amazon.com/How-Make-Sale-Frank-McNair/dp/1402204....