By now they could well be subsumed in e.g. Steve Blank's work, but it's not a long read and the price is right. And they walked the walk: they developed a device that the could fabricate on a lab table top, but it required different thinking from hardware designers. That plus their quasi-pivot (actually just doing the numbers and figuring out which of the two businesses they were doing (selling parts and consulting) they should focus on) are also worthwhile, even or especially if you're in software.
4 Steps to the Epiphany is a phenomenal book on selling new b2b IT products.
Secrets of Question-based Selling is the best consultative sales book
SPIN Selling by Neil Rackham is also quite good
Tested Advertising Methods and Scientific Advertising continue to be two of the best books on copywriting, despite being very old.
Your Marketing Sucks - Mark Stevens - Short Read.
Persuasion Mastery: 500 Practical Lessons In The Psychology Of Sales - Stephen Thieme - Long One:)