I have just finished the third and final season, and thoroughly enjoyed all of it. When adaptations of books, either as a film or TV series, stick faithfully to the source material, then generally you get a good result.
All the cast are on top form. Dafne Keen is excellent, James McAvoy is always brilliant, but top marks have to go to Ruth Wilson as Mrs Coulter. Her character is just magnetic and she conveys so much complexity with just the slightest of expressions - it really is an acting masterclass.
I won't discuss the plot, but will only state that the multiverse concept is very well portrayed, the character interactions are written with style and care and the 'demons' are beautifully and realistically rendered.
And I couldn't resist the irony of my review title... :-)