Unless you do this effectively, hidden notes and files are best saved for extra material. Don't have your main plot only understandable through copious amounts of reading. People play video games instead of reading a book because they want some level of interactivity. But I love the added experience of finding out WHY and HOW and what else has gone on. And like Pete says, Dark Souls is great in a really minimalist kind of way, but that doesn't work for every person or every game, so you've gotta be careful.