That's probably the easiest access one but for a less cluttered one the UP has bare bones runes like dungeon entrances, towns, hunting spots in Ilsh and tokuno, and a rune to the Abyss and some other things. Along with a T-Map rune library.
PGoH copied alot of the luna Library and reorganized it by colors and cut alot of the stuff not many people are interested in. and set it up in there town.
I personally use UP's library because it's simple, easy, and I don't have to look on several levels of books to find a runebook that may have a rune I need. For obscure I usually head to PGoH and as a last resort I go to the luna one and search.
Now I'm not trying to insult the Luna library I just don't like navigating it and luna causes more lag.