I was disappointed that some of the content has been available previously. Not near as much recycled content as Humans of Golarion had, however.
From a crunch perspective, variant Tiefling Abilities, variant Tiefling Heritages, Random Tiefling Features are all straight from Bastards of Erubus.
The book also has new subdomains, curses, inquisitions, traits (incluing for the variant heritages), 14 feats (though two are again from BoE) and a sorcerer bloodline. I may have missed some cruch, and some of these could be from other sources too.
There's a lot of fluff on tieflings, not sure how much if any of that is reused.
So, it's really a mixed bag,
