Book 1 definately was the best. George and Orry formed a binding friendship (better then w/ their own brothers) and met their true loves. George and Constance had a marriage, that while not perfect, was one full of love and respect.
Book 2 second by a narrow margin. It had the suspense of when George and Orry would meet on the battlefield, plus completely reconcile. My favorite? Orry killing Justin and able to marry Madeline.
Book 3 did have good moments. Charles and Willa were my favorites. George and Madeline was too damn weird and I mostly fast forwarded through most of their scenes. I just hated that so much was cut out from the book. I know PS didn't want to come back, but w/o Orry in the film, wasn't the same. The book was okay because it fleshed out the characters more and ended in 1877, but killing Constance was horrible! Couldn't they have left her in or if they had to kill her, wait until near the end? So much story potential there. I'm just glad George stayed true to her until he died.