First of all, I must confess that when "Good Omens" premiered, I didn't remember much about the plot (and that allowed me to watch the adaptation with a neutral point of view).
Once I finished it, however, it wasn't necessary for any demon to tempt me to reread the book written by Terry Pratchett and Neil Gaiman... I really wanted to find out wether the adaptation was faithful or not, because I loved it!
In fact, the miniseries hooked me progressively, up to the point I couldn't resist watching the last episodes in a row to find out the ending.
I would say that "Good Omens" makes you feel something that only happens with the best books... once you finish it you need to go back into the story to spot all the hidden references and winks.
Honestly... I believe this is one of the most faithful adaptations I've ever seen. The dialogue and the scenes are practically identical, the performances of the entire cast are great...
On the one hand, descriptions are what I like most about the book. Pratchett and Gaiman know how to condense the human nature into very few lines, and the narrative voice is so funny. In the miniseries certain parts of the narrative voice have been mantained, but it focuses on the visual language instead, which makes the story even more spectacular.
There are some characters that doesn't fit the original description, but their personality is exactly the same, so it's not the end of the world (quite literally haha ^. ^). And speaking of characters...
a) in the book you'll learn extra information about some minor characters (actually, there are more of them, but I didn't miss them)
b) in the series you will meet completely new characters, and connect and empathize more with the existing ones (after writing this I just read an interview where Gaiman says this was his intention).
The final scenes are quite similar, but the order is slightly different (just like the rest). Since Aziraphale and Crowley (played by Michael Sheen and David Tennant) now have even more prominent roles, the fact that their scene is the last one of the miniseries (along with a very special song mentioned in the book) seems right to me.
As a matter of fact, people couldn't believe Sheen and Tennant hadn't worked together in the past, and now I understand why. The chemistry between them is almost tangible, and they make the characters of Aziraphale and Crowley shine.
Since Good Omens premiered, the relationship between the aforementioned angel and demon is subject of study. In the book they are clearly two old acquaintances who have more in common with each other than with their peers.
Although... the miniseries goes much further. Seeing how they protect and care for each other in the midst of a terrible moral dilemma that keeps them from being together, I can only say that the feelings they have for one another are... ineffable.
book vs miniseries
I truly think that "Good Omens" is a divine adaptation that blends perfectly with the book. I would even say that it expands its universe and gives it a new dimension. From now on I believe I'll only be able to imagine it this way.
Watch the series and read the book. My Spanish edition of "Good omens" (timunmas 2009) includes an interview with Neil Gaiman and Terry Pratchett that deeply moved me, where they were asked about a future movie.
Long afterwards, Gaiman adapted the novel with a single rule: create something his friend Terry would have enjoyed. He explains he started writing the script right after returning from Pratchett's funeral.
Do you want to know what they said years ago in that interview? Well, I'll end this post with their answer to the question...
«Will there be a movie, then?
Neil is excited to think there will be one and Terry is sure that will never happen. Either way, neither of them will believe it until they're sitting at the premiere eating popcorn. And, probably, not even then.»
Yes, I'm sure Terry Pratchett would have loved this adaptation of "Good Omens".