Jeremy, on how he thinks about building progressive web apps:

In my opinion, the term “progressive web app” can be read in order of priority:

1. Progressive—build in a layered way so that anyone can access your content, regardless of what device or browser they’re using, rewarding the more capable browsers with more features.
2. Web—you’re building for the web. Don’t lose sight of that. URLs matter. Accessibility matters. Performance matters.
3. App—sure, borrow what works from native apps if it makes sense for your situation.

He also links to Jason Grigsby’s Designing Responsive Progressive Web Apps which is another great read.