A fascinating guide to the huge wealth of talent behind the League setting. Beautiful art, detailed worldbuilding, a handful of short stories that are satisfying and attention-grabbing. Definitely worth picking up if you're at all curious about the setting.
I only have two gripes: one, that not every region has all that much detail (Demacia and Noxus have like 20 pages each, the relatively new Ixtal has about 4, and that makes sense... but Bandle City only has two pages total??) and two, that a few of the short stories rely too heavily on League characters.
I know it seems strange to criticize the League worldbook for having League characters, but the best stories are the ones that focus on the people, and their lifestyles and day-to-day struggles. The Noxus story is probably my favorite - it details a recently-conquered town as its people adjust to life under a new banner - and I don't think it mentions any champions by name at all. Even so, you get a sense of what the regional culture, the attitudes toward what's good and bad, what made the region strong.
And then you have the Shadow Isles story, which is a murder mystery that the reader will either solve immediately (if they're at all familiar with the games) or be utterly confused by (caution, this paragraph contains spoilers). There's some good worldbuilding early on, as the characters go through their daily routines, showing why they choose to live in such a dangerous area, and then... gasp! All the boats are trapped in chains made of blood! And people are dying! "Oh by the way," says the mysterious aristocrat, "my name is Vladmir." If you're familiar with League, the story's tension is immediately gone. If you aren't familiar, too bad, the story assumes you are and never goes into detail on who he is or what he can do, it just shows you the effects of what he does and assumes you'll nod your head and say "yeah, that's Vlad for you."
I know I spent a whole paragraph on one negative thing but there's so much good in the book beyond that. Cool concept art, history (including a historical timeline!), and lots of details on the lesser-known bits of lore. Definitely worth picking up.