It works on both levels though. It's also a big plus that the chase up the mountainside actually takes place in a real place. There really is a Cloud Peak and it's just as Johnson describes.
In the previous book the author gave the readers what they wanted; a full ensemble, a light humourous tone and no damn flashbacks. Walt's propensity for getting a bit beaten up was duly sent up but in Hell is Empty Johnson takes things to a new level and it's no joke. But Walt's wry style of humour is still there. Walt wouldn't be Walt without it.
I do wonder though how things would have turned out if Sancho had plumped for The Poems of Emily Dickinson.