Unread Books Glow
This mod is similar to Glowing Ore Veins 300 and it's just as useful.
Skyrim is full of books to read and its common to open up a book you've already read. This mod ensures that that won't happen.
With Unread Books Glow installed on your Xbox One (sorry, PS4 owners), books you haven't read will glow a different color so you don't waste your time opening the ones you've already taken a peek at. Once you've read a book, its glow vanishes.
Unread spell tomes are green, skill books are red, quest books and regular books come in various shades of blue.
The mod tracks all of the books in the game though books your character has read before installing the mod don't count. You'll need to read them again.
There's now a remastered version of this mod if you're interested.