There's some great writing in the grimoire, and following stats does help you with gaining resources in certain places, something that's handy when you start leveling up legendary items. I really wish you could read them in game, but the app is nice. RSebire's idea of printing them has occurred to me a few times, and I'll probably follow suit. The ghost fragments particularly add a lot to the story, and I've turned a little obsessive into finding ghosts. So far, I've only found 12 out of the 50 or so that are hidden around the universe. I'm probably going to run a second Titan or maybe a Warlock to go find the first two that I missed in the start up of the game. Apparently some are only available during strikes or storylines? I haven't heard that confirmed, but I know that certain areas aren't open outside of certain times.