I rarely ever read books in games... unless they're written well and are interesting.
The Elder Scrolls tends to have these the best in my opinion. Not the "Lore Building" stuff. No, the fun stories. The things that tell you a story. I don't care about the "how I discovered you could put two enchantments on an item" books. But, the book about a thief who tried to learn water breathing so he could rob a sunken ship... and he drowned? Surrounded by a ton of potions of water breathing? I liked that story, it was good. I read it. I also enjoyed reading "The Lusty Argonian Maid". Lots of fun wordplay in those books. In general, I tended to read any of the books that were simply telling a story in the world.
I don't really care about books I read that are like, "Oh, the reason there are three moons in the sky is because..." Yawn, snore fest.
Now, one subject of Lore in Elder Scrolls I enjoyed reading, was anything to do with the Dwarves. They vanished. Without a trace. Nobody knows where they went or what happened. It's a mystery. That, in and of itself, makes studying it quite interesting. Nobody can reproduce their metals, so there's no new Dwarven Metal anything. Everything is just melted down existing Dwarven Metal and reshaped into new weapons and armor. That's interesting too. So, I tended to read the books about the Dwemer.
Beyond that... I don't really care about your Lore. Introduce your Lore through the story or character dialogue. If I'm going to read a book, it needs to serve a purpose.
It needs to:
1. Entertain.
2. Cover Something Interesting.
Or...
3. Provide Quest Hooks.
If it doesn't do one of those things, I tend to pass on by.
Just because you want to tell me all the Lore of your world, doesn't mean you should tell me all the Lore. Tell me only what's relevant to your story. Or, what's relevant to answering a Question I may have. Mass Effect did a good job of that. I avoided the Codex for most of the game... Until I ran into a question: "How the heck does a Mass Relay work?" I went looking. Game explained it to me. Anytime I was confused or had a Question, the game had a place to provide an answer to me. But, it kept it all someplace I could view it if I wanted to. And, you know what? Nearly none of it was necessary to the plot at all, so the game spent zero time telling you to read a Codex or giving you any information in the world that had to deal with the Codex.
If the game had told me, "Oh, read this book if you want expansion on the Lore", I'd have probably passed.