Good:
- The casting is excellent. Tennant and Sheen are wonderful.
- They got Queen for the soundtrack!
- Lots of neat easter eggs. Great intro animation too.
- The series very closely follows the events of the book.
Bad:
- Some of the cast aren't really put to good use. Jon Hamm is a fantastic comedic actor but his Gabriel is pretty bland and one-note.
- They don't really explain the Queen joke very well, in fact a lot of the humor seems to be rushed and doesn't land well.
- It seems to lean heavily on "look how silly this is" as the main source of comedy.
The book was a cleverly-written story with hilarious descriptions, prophecies, and footnotes scattered throughout a silly plot. The series faithfully recreates the silly plot for the screen, but a large portion of the novel's humor didn't survive the translation to a visual medium. God-as-narrator attempts to carry some of the witty commentary over, but it's not very effective. The show just seems to do a lot of hand-waving, "Trust us, this is all very clever but we've no time to waste - there's more plot to cover!" Many of the punchlines are there, but the joke setups just got lost in the mad dash to check all of the fan service boxes before the credits roll.
If you want to spend 6 hours watching a new book adaptation then I'd suggest Catch-22 on Hulu instead.