I read the Barchester Chronicles for the first time when I was about 12, and for some reason I just kept ploughing through, at the same time enjoying yet finding it difficult to process. I've since read the first two books a couple times each, and each time I read them again I enjoy them a little more. Clever, interesting, and deeply political, they have wonderful characters and also provide a great historical view.
(Plus I love the Warden. He's lovely.)
The Barchester Chronicles (dvd series) is also really well worth the watching.