O'Reilly has a very generous timeout period of 24 hours, so unlike some other databases the PG Library has that have 30 minute - 2 hour windows, ebooks and other content in O'Reilly can be kept open for 1 day before you'll be asked to log in again.
However, sometimes 24 hours after you started a session, even if you closed that browser tab, you may see a "403 - Forbidden: No Access" message when trying to access content. In these cases, restarting your browser and logging in again should be sufficient to fix the issue. In severe cases, try a private browsing session or delete your browser cookies/cache.
To view a book:
The video player in O'Reilly is similar to other video players you've likely come across. Standard options include the ability to scrub forward or backward, change playback speed, enter a full-screen mode, and see closed captions.