(6) Tree Line
Look at it this way: Gone With the Wind is one of the most popular books ever, so it can't be that hard to get through. To this end, it's written clearly and its plot bounces along. On the other hand, it is very long, and has lots of characters and events to keep straight as you go. This places it up there at the tree line—a doable hike for sure, but not exactly a jog to the summit.