Kindle does need mobi files but if you're finding only epub instead in the books you want (epub is the standard open format for most ereaders not made by Amazon; good torrents will have both formats but they don't all), I recommend Calibre for converting the format to mobi for your Kindle. Calibre is free to use and a good computer-based organizer for ebooks; I actually use it exclusively to load up my Kindle, too, not only because it converts formats for me but because it's an easy way to get fanfic onto mine. ;)

I'm not sure I have any book recommendations! A lot of kids liked those Lemony Snicket books back in the day, though, how about those? And the Eragon ones were popular, too. Disclaimer: I personally haven't read either series, I just know they sold like crazy.