I'm a huge Pratchett fan, never read much Gaiman (though I hear Sandman is fucking excellent, but never got around to reading them) and I love this book to little bits. The relationship between Crowley and Azriphale is probably my favorite thing about the entire book, the idea that an Angel and a Demon would have more in common with each other than they would with their respective bosses is a great concept, and the references to the 14th century crack me up.
Also, the idea that every single tape will eventually turn into a best of queen cassette if left for long enough in a car is hilarious. I'm thinking of picking up Anasi Boys next week to see how Gaimans individual writing style is, because I picked up a lot of Pratchett influence in Omens, but I couldn't distinguish what Neil had done.