My Chinese is not good enough for translating yet; give me, say, 10 more years in snowy Harbin and maybe I'll try...
Why would people read pinyin? Well, because, well, actually, you're right, it would not make sense since the book would be for chinese people who can all read hanzi. But it would be nice to learn Chinese that way, with a pinyinized copy of Lem. "Wo ai ni Hari!" "Wo ye ai ni Kris"! etc, etc.
Cheers, Socrates