Mass Effect told the story through the missions and fully explained and devolved the current storyline through gameplay and conversations with the characters. The Codex was for background information on the different alien races. Their history, biology, government, etc... As well as your version of Commander Shepard's story. Also including the entire system of pseudoscience that they created to explain how things like the Mass Relays and Element Zero cores worked. This is not the case with Destiny. The story missions don't link and flow together like a story is supposed to. You just go from one random thing straight to another. Nor is the storyline of what's currently happening ever said in the missions or cutscenes. Example, "I could tell you of the great battle fought centuries ago." This line is said by the Speaker and he just leaves it at that and moves on. Ok great, so you want me to go fight but what am I fighting, who am I fighting, and why do I care? Tell me about this great battle! Another example is the line, "I don't even have time to explain why I don't have time to explain." Really? This random character shows up, hops in our radio frequency, and tells us to go to Venus. We get there and find her, and she tells us nothing. Absolutely nothing to progress the story or to even start one. The grimoire tells us the story as well as background information, the lore, and the history of the different races. However we shouldn't have to leave the game to learn the story. It should be in the, you know, story missions and cutscenes. Hence the name, story missions. Everything else being in the grimoire is perfectly acceptable though.