When I finished reading this book for the first time, I immediately flipped back to the first page to start again. This was partly because two-thirds of the way through my first read, I looked at some reviews of the book and realized how many details and jokes I missed. The book started out great, but lost me in the middle, where the introduction of multiple new characters slowed down the plot, and Crowley and Aziraphale disappeared for pages and pages, and then finally showed up near the end for a good, if a bit anti-climactic, finish.
The second read was much more enjoyable, now that I was already familiar with the characters and the plot. I read more carefully this time, caught a bunch of things I didn't get the first time around, and was generally entertained. The book pokes fun at a lot of things in life while also being surprisingly insightful at times, and I didn't find it tiring or boring to reread so soon after the initial read. I think Good Omens
is probably one of those books that can be read over and over again and is still enjoyable, even seems fresh, each time. (I'm pretty sure that even after two reads, I still probably did not get half the jokes.)
Crowley and Aziraphale are by far the best characters in the book, and sadly, I founnd Adam one of the more boring ones, despite being very important to the plot. I think the main problem is that his scenes don't contain much action, he just sits around and talks to his friends, but their discussions, while somewhat amusing, are nowhere near the level of entertainment of Crowley and Aziraphale's banter. The same goes for Anathema, Newt, Madame Tracy, and Shadwell. I felt like a lot of their scenes ran on a bit too long because half the time Pratchett and Gaiman are setting up for a joke, rather than moving the plot forward. I did appreciate their humour, but sometimes it's just a bit too much. However, I did end up liking just about every single character, and even Adam's scenes were not that bad the second time around.