I could probably fit a couple of bookshelves in my Honda Insight, but I've made some modifications that increase interior cargo space. It also has no back seats. The stock engine was EPA rated at 70mpg highway. Driving slowly (~50mph) I was able to consistently get ~100mpg in fair weather.
Something larger? In my mind, hands-down a VW TDI wagon, or a Prius (Prius V?).
Something newer? I'd likely give a Hyundai Ioniq PHEV a shot. Looks like you can find them for around $9,000 with reasonably low miles. They have a rated 29 miles electric range, and some trims of the Ioniq have as high as a 60mpg combined EPA rating when burning only gasoline. 29 miles EV + 60mpg afterward is tough to beat.
