The first three books, for me, where probably the best when considered together.
There were other great books in the series, but those three stick out. The rest of the series becomes very meandering and a lot of story lines don't feel like they go anywhere. GOTM, DG, and MOI have tighert story arcs and there isn't quite so much going on, which to me makes it easier to focus on what's important.
Last few scenes in DG with the chain of dogs & Coltain... Amazing.