Pyre

In the wagon there is a book that you can read to get some background on the Pyre world. As you play through the game pages in this book automatically unlock. In order for this trophy to lock you need to actually inspect each page that unlock to a total of 50 (you must click on the inspect button for the page to count towards your tally).

This trophy should pop up naturally but to help you, make sure you visit as diverse a selection of locations as you can and have as many conversations as you can in the wagon and this should pop up without any issues.