Yes, Nicholas Sparks was involved in every step of the creation of the movie, and agrees with the changes. He consulted with Karen Janzen during the script writing process, visited the set 3 times, and consulted with the director after it was filmed.
On his website, he said:
"I'll go on record as saying that I love the movie. I think it's a wonderful adaptation, and I hope that everyone who enjoys my work will head out to see it. I promise that you'll enjoy it."