Middlemarch
This is probably the best novel you'll ever read. It's action-packed - but all the action is psychological, and it is described in great detail by Eliot, so that we know exactly what motivates the character to act in the way they do. The power of this novel is in its gradual unfolding of the personalities and thoughts of the people whose stories Eliot tells, and in the gentle yet relentless increase in drama and tension, until the final climax when all is resolved. If you haven't read this, make it the next on your list.