For GMs, the book is woah. 85 new undead monsters, gazetteer of undead lands of Golarion, an adventure, new haunts, lots of stuff to play with.
Special shout-out to the ghostly luchador and the return of night-things. Flying undead level 20 sharks ftw.
For players, there's some great stuff (skeleton ancestry, "regular" archetypes, items) and the heavily advertised undead archetypes which are fun BUT require special handling, because a bunch of level 1 ghosts could be too much for a regular adventure to handle.
It's 4.5 stars BUT I add 0.5 extra for the book tying into South American approach to death and a nice dusty pink/flowers/skulls theme instead of the done to (un)death "black, sick flesh, grey, death, angles and bones" theme most RPG books about undead use. A nice breath of freshly stale grave air.