Let's all pray thay there will be a sequal but as far as I research about the authors, it's almost impossible. Ugh. This is so good. I mean for me, one of the few fantasy TV series that has a canon ship. If possible, I wanna watch Crowley and Azir's whole immortal life. Actually mutual pinning each other for 6000 yrs. Lovely old married couple.
as far I know the show covered everything in the book so there is a low chance of a season 2 but I've seen reports that Neil Gaiman and Terry Pratchett had planned a sequel for the book so a season 2 isn't necessarily out of question.
from what I read it seems like Amazon is looking to use some of the content of the planned but unreleased sequel to make a season 2 but at the moment nothing is concrete. so let's hope something gets announced soonish~