This comment is to suggest some things that would make Notebook a great replacement for Google Keep for me. You've got most of what I need, and the app looks great on my phone. Now...
1) Ability to share a note for joint editing...the household grocery list between me and my wife is my #1 reason for this and probably the most important thing I use Keep for because me love food.
2) TAGS.
3) Minor nit to pick but...ability to manually organize notebooks on the web page.
4) The much-desired desktop app for Windows.
5) A post by the developers, updated regularly, showing a list in order of priority the different features like the ones I listed above and their development status. Please don't be like Google, being stingy with what's going on. :)
I'll update this post if I think of anything else.