Turtledove's Atlantis. Forgive me if this post is too long and threadjacky, but I can remain silent no longer.
1. Forget the Phoenicians and the Vikings. Here's a place that's within three weeks sailing from Europe, is discovered in the mid-15th century and isn't monopolized by the Spanish. Here are just some of the waves of immigrants it could have seen:
Germans fleeing the aftermath of the Peasant War.
Germans fleeing the Thirty Years War.
Huguenots fleeing Louis XIV.
If any of these people settled in Atlantis, they didn't tell Turtledove about it.
2. At first, all we learn about the teachings of the House of Universal Devotion is that God loves us all and wants teenage girls to get busy with dirty old men. I was expecting to find out that "the Preacher" was William Blake, teaching the gospel of the Four Zoas, which would have been Crazy Awesome. Instead, I found out… not a damn thing.
3. Remember that guy in the black cape at the beginning of the third book? He's all like "I am a Secret Agent!!!" and then he just disappears and we never hear from him again. Didn't Chekhov say something like "Never introduce a Highly Visible Ninja in Part One unless he's going to off somebody by the end of the book"?
4. The Atlantean Army in Book Three. Led by two guys who command on alternate days, who have radically different agendas, and both of them are lifelong civilians? I know it's kind of like how the Romans used to do it, but there's a reason why they stopped. Twelve legions of angels with flaming swords and AK-47s couldn't win a war like this.
5. Speaking of the comedy duo Newton & Stafford… I swear every single conversation between them goes the same: "WAAAH! I WANT MY SLAVES!" "You can't have any slaves!" "BUT I WANT THEM!" "But they want to be free." "I DON'T CARE WHAT THEY WANT!" "But you have to care what they want, because they have guns now." Seriously, do either of these guys have families? Hobbies? Favorite sports? Secret sexual longings for each other? Anything to talk about other than rehashing the same ground over and over and over again?
There were moments when if Sam Carsten had popped in to complain about his sunburn, I would have breathed a sigh of relief.
6. And finally — I can't believe I forgot this — in four hundred years of settlement, not one person ever thought of DOMESTICATING honkers???