A lot of sci-fi is rather grim stuff. You'll find interplanetary wars. You'll find fascist societies with evil overlords. There's Loss of life and deception etc. But it surely’s not all doom and gloom. The evidence may be the beloved (and infrequently adapted) series of books beneath the blanket title http://young-adult-fantasy-books43197.blogolize.com/Rumored-Buzz-on-Science-fiction-novels-50660631