Yes! If you start reading/listening on one device, you can jump over to another device without losing your spot. Just make sure you have a strong WiFi signal on both devices so your reading/listening history is saved and available to be reopened.
When jumping between networks or between online and offline reading there can be syncing issues between devices. For instance, if you read ahead on one device while disconnected from the internet and then start reading on another device that is connected to the internet, you will pick up at an earlier place in the book. Ensuring a strong internet connection is the easiest way to make sure the titles and reading spot is kept between devices.