Can't help about a book I'm afraid, but happy to give our 3 cents worth. Many people will disagree with us I'm sure, but.....
Last Christmas/New Year, we had out first visit to Universal, and although we all enjoyed it and will definitely be visiting again, for us it's not a long stay option, probably 3N/4D at most, whereas we can easily do 3 weeks in Disney. The rides, particularly the thrill ones, are excellent and the HP area is really cool and well done, but it doesn't have the same atmosphere. As well as the rides we like to just chill, people watch and take in the shows&fireworks in Disney, we found Universal to be less relaxed in that respect. We did stay on site, so had the benefit of the express pass (NB does not work for the HP rides), which is wonderful. There is not as much planning involved in Universal, that is for sure, and for some that, in itself, could make it a more relaxing holiday, no meeting FP+ times that had been scheduled months out etc. Even at Christmas you really didn't need reservations for restaurants, with the exception of Mythos, most had plenty of free tables. I really can't put my finger on it, but we always felt you had to be going to the next ride and most people 'seemed' to be rushing around doing just that. Overall we thought the food was better, the rides excellent, the Hotel (Hard Rock) was fab, and we did really like it, just not love it. But, as I said earlier we are going back.
I did a trip report
http://www.disboards.com/threads/home-again-another-great-trip.3368796/ also.