This series undoubtedly deserves the place among top ten manga titles, which it currently has on MAL.
Though the film is failry good, it does not cover even half of what is depicted in manga. There are a lot of post-apocaliptic series about humankind trying to make ends meet in severe conditions of wreched world. But they are not as deep and moving as this one. Of course, you should keep in mind that bringing up a topic of world's balance, of our race's place in it, is Miyazaki's forte, be it manga or animation.
This series not an easy read, it has a lot of ideological clashes. However in contrast to all the violence and agression we have right now emerging in manga, Nausicaä of the Valley of the Wind remains a pivotal oasis of its genre.