reader's companion and atlas are good to go along books if she doesn't have any. I at least just love the more detailed maps found in atlas depicting some of the key events.
David Day's beastiary has some amazing illustration as well
Well I've heard that some of the lore found within it was not accurate? But I can't tell what those are out of the top of my head. I just recall reading it along the Unfinished Tales and Lord of the Rings trilogy back in the day. And found it extremely helpful.
Feel free to correct me in the comments what parts of his book are not accurate to the lore.