I tried to come up with books I hadn't seen mentioned already. All of these are loved by most of my friends.
Fantasy: Brandon Sanderson's Mistborn, then the other two books in the trilogy, and the stand alone, Alloy of Law. It's fairly clean, and has an amazing magic system
Sci fi: Lois McMaster Bujold's Young Miles, from the Vorkosigan Saga. My favorite sci fi series. It is a bit mature, and has some mature themes, but I haven't come across a graphic scene.
Christian non-fiction: Anything by Cloud and Townsend. Many people in the church are already familiar with the Boundaries in Dating series, but I would recommend the general Boundaries book, as the principles can be used for just about everything in life. I also recommend 9 Simple Things You Must Do by Henry Cloud.
Christian fiction: My recommendation for Chris Walley was already mentioned, but I'll second that. It's really hard to find good Christian speculative fiction.
And, I won't link it or anything, but my book Surfer Girl is on Amazon. Despite the name, it's fairly unisex. It's a spy novel, clean, and has quite a bit of action. It has enough reviews that you can get an idea.
Christian female geeks, gamers, and fans