Here is a playground that should read as book about the Combine framework, but with the added benefit that it is a playground and you can get your hands into the code if you want to.
It should enable you to discover Combine by playing with it and going through simple exemples.
This does not have the pretention to cover all of combine, I do hope to find the time to add more content to it in the future.
If you see a mistake or something that seems imprecise do not hesitate to reach out to me, either by opening an issue or directly through twitter. I am definetly open to any feedback you might have.
This is free to use for everyone.