When I tried to speak about this book, I failed miserably.
I just couldn't summarise the whole plot in a few sentences, because there's too much awesome stuff going to decide what to begin with.
Then, about a year ago, I decided to settle on this:Good Omens
is a book about an angel and a demon who have grown too fond of Earth and its inhabitants. So when Crowley, the demon, receives orders to place the Anti-Christ in an influential human family, the two decide to thwart the upcoming Apocalypse.
If I had to go full-on lit teacher mode and find underlying themes for this novel, I'd say the most important ones are: the nature of good and evil, freedom of choice and how it affects "destiny", and, of course, ineffability.
It was written by two of my favourite authors ever: Terry Pratchett and Neil Gaiman. Of course, if you know the former, you already expect it to be incredibly funny.
It is. But it's also heart-warming and an all-around brilliant book.
I'd recommend it to everyone, but I know a few people who didn't especially like it. I can't quite put my finger on what those I've spoken with who didn't like it had in common, though.
Pro tip: I'd suggest getting a copy with some extra content (eg interviews) because they're extremely fun to read.