I've bought this book and I am very disappointed. Instead of a couple of good rules which allow to create characters of mixed acestry and/or a different culture (like Pathfinder 1e did in the 'Advanced Race Guide'), this book simply gives us just some examples how to split the a D&D 5e race into an ancestry and a culture (something 5e already did with most races). And they put the ability modifiers in the culture! This leads to the weird effect that a halfling raised in an orcish culture will be stronger than an orc raised among halflings.
The only good thing about this book is most of the art. The rest should be replaced with sensible rules which allow DMs and Players to create their own species (I prefer species to ancestry because fantasy races are different species and not simply just different races or ancestries) and cultures.
EDIT: I came to the conclusion that the extremely long and extremely biased preface full of disproven "facts", the lack of rules explaining how to create your own ancestry and culture packages and two poorly written adventures do not counterbalance the good idea and the great artwork by Talon Dunning.
Even if you like the idea behind this book, do not buy it. It lacks everything which would make it a decent rule book. Everyone with some experience in D&D 5e could write much better house rules! This is a book with a political agenda disguised as a rule book! And that's the main reason I lowered my rating from two stars to one!
2nd EDIT: Buy "Tasha's Cauldron of Everything" instead. The rules for modifying your origin are much more sphisticated than this one. WotC did not made the mistake moving inherent traits to cultures. And this official rules give you much more freedom with the ability modifiers and proficiencies you gained from your origin.
The introduction ignores for example that Tolkien wrote that "[they] were all orcs in the great war". This simple sentence makes clear that Tolkien's orcs which according to his own mythology were created by the great enemy by torturing elves were never based on specific people but on his experience as soldier in the World War I, a war that shaped his view of the world and also shaped his mythology. Even if he wrote that he hated allegories and that "The Lord of the Rings" is not allegorical, you could argue that Tolkien's orcs are an allegory for the worst human soldiers can be.
[1 of 5 Stars!]