O'Reilly content is organized in Topics.
On the main toolbar, expand Explore, then select All Topics.
You can click on topic names (Business, Career Development, Data etc), and drill down (example: Design > Design Process > Design Thinking). You can put a word in the search form (no need to click Enter), and you will see a new list of topic names that you can click.
You can filter the list of items in a topic by Popularity and Formats.
Under Topics You Follow you will find a list of your topics. Click the topic name to see the items, you can then sort the list by Date Added. Click X for a topic if you would like to unfollow.
To find a topic to follow, either write words (for example Operating Systems) in the Topic search form. Or first click System Administration, then Operating Systems. Then click the Follow This Topic button.