I'm a big fan of Fog Creek's "The Most Basic Things Your Company Needs to Know About Sales" (https://www.fogcreek.com/guide/The-most-basic-things-your-co...) It's roughly 25 pages about high level sales strategies. The PDF mentions the book "How You Make the Sale" by Frank McNair (https://www.amazon.com/How-Make-Sale-Frank-McNair/dp/1402204... was a great 101 level book on sales. It's high level so it could be applied to everything from selling cars and real estate to software.

I found these helpful because it was less "here's 10 closing tips and tricks!" and more about the sales process.