Oh my goodness yeah, I've read the book, but it was quite some time ago and I can't remember all the details.
Spoiler for the book:
The setting is really similar with the walled town, birds flying over the wall, the town in the middle, the river and the novel even has an abandoned barracks, but a huge difference is that in the book nobody leaves the walled "end of the world". I feel that the walled town in the book is a form of escapism and hence was rather disturbed by its ending. After the main character had tried so hard, he finally decides to ?give in and stay in the town? Whereas in the anime
So I don't really know if we can come to a greater understanding of the anime thru the book...
Of course like I said I can't remember the finer details of the novel right now and if you can draw some parallels between the book and the anime I'd be interested to hear, um read.