Here's a great tour of the interior of a "4-Wheel Camper" style pop up slide in truck camper from Phoenix Campers.
Not only do I love the general shape of this style of pop-up truck camper -- both for its flexibility and the gas-saving aerodynamics relative to other RV designs --
I particularly love the way Phoenix has managed to fit so much in a tiny space. (Note the combined shower/toilet stall!) Since you're trying to make a livable space out of approx. 30 sq. ft., it really inspiring to see them getting creative like that.
Personally, as a Do It Yourselfer, I also love this design for a DIY truck camper. Click to read more about my favorite camper design on my blog.