If your web app is your primary project, then that should be your design canon. In other words, your standards should be encoded there. This is discussed elsewhere in the book.
Any style guide or marketing project should reference those standards. They shouldn’t maintain their own separate standards, just like you shouldn’t maintain a separate version of your site in Photoshop. Can you imagine if the web team, the marketing team and the designers are all maintaining their own design canons and trying to keep them in sync with each other?
If you can, then you can imagine the average modern web development project.
Marketing material obviously doesn’t have to follow the same exact rules as your product. But some stuff should be the same, like brand colors and the tone of the writing.
But standards aren’t why you suck at marketing. Making your standards available to your marketing team in the form of a style guide is barely any work at all. No, you suck at content (It’s too late to change the chapter name!).
Specifically, you suck at putting marketing content online in a way where it’s easy for marketers to maintain. I know this is true because this book has CSS in the title, so you’re a web developer or web-developer-adjacent. This means you’ll have some fundamental disconnect with the marketing team when it comes to content management. They’ll want to do too much. And you’ll want to do too much too but in a completely different way.
Do you use WYSIWYG? Markdown? Dreamweaver? Almost anything puts an extra layer into the process. And that means more maintenance. Some developers cherish this opportunity to “help” the marketing team with some much needed technological heavy lifting.
Avoid those developers.
CASS lets you just use HTML. So use that. Go to Markdown if you have to. WYSIWYG if you really hate yourself.
If you subject the marketing team to your insane world of learning things to avoid tech debt, you can never go back. You just have to do that forever.
Subjecting marketers to this is even more evil than subjecting developers to it. They just can’t cope.
If you do find yourself in a situation where the marketing team is confronted with raw HTML, then CASS is a blessing. All of the class names will make sense. It’s copy/paste friendly. It’s words.
Of course that doesn’t mean the less-technical user can’t still do damage with it. It won’t be contrast damage, at least. Probably. The important stuff will all still work.
Never underestimate what a user can put into a textarea.
The Gumroad version contains a secret chapter that spills the dirt on CSS preprocessors, a tech CASS no longer uses.