I have a system that involves content lists (as I call them). I use Things by Cultured Code and some time ago I'd been using it with these kinds of lists too. Here how it works: I have a list (project) Books to Read, which contains tasks like Farewell to Arms by Hemingway. When there is the time to start reading a new book, I create a project out of the task and fill it with names of chapters. Then I gradually work through the chapters. The only problem with this system is that it is a little hard to maintain and not to forget to update other services (checkin in Foursquare when visited a place or such).
The other approach is to use separate services for content lists iTunes Wishlist for music, IMDb and Netflix list for movies/series to watch, Foursquare for places to visit. But then there is a problem of forgetting to check these services from time to time. I wouldn't probably forget about GoodReads, Netflix or iTunes, but I keep forgetting about iMDB. I partially solve it with repeating tasks to buy a new album once a week (I do it so to limit spending) or daily reading "session". Still it makes the system a little too clumsy.
In the nutshell the question is whether to introduce outside services to your GTD, or go with all-in-one approach. I know it's kinda subjective, but it would be cool to hear some opinions on that.