OK... I get that you need to find drops to get the Advanced recipe books. After level 19, aren't there any Essential recipe books anymore? If so, are they also drops? If not, where do you get them?
Yes they are drops but they will a new name based on your class choice at lvl 20. So there are no craftsman, outfitter or scholar books post lvl 20 only tailor, woodworker, sage etc.