The first seven books of A Series of Unfortunate Events followed the same formula. The Baudelaire Orphans are with the banker Mr. Poe until he can find a new relative willing to care for the siblings. Things go badly and the evil Count Olaf shows up with another nefarious plan to kidnap the children and somehow steal their inheritance. In the end they get away and Olaf is on the run from the authorities. The ending of The Vile Village changes this. The Baudelaires are on the run, suspected of the murder of Count Olaf despite the fact that he isn't dead and that there is no way they could have committed the non-existent crime. The Hostile Hospital opens with the orphans trying to find a place where they can learn about VFD, the Quagmire triplets, and some clue that will help keep them safe and stop Count Olaf from coming after them ever again. This time there is no Mr. Poe and no new distant relative to live with. Count Olaf is in much less of this book than we have come to expect, though he and his cronies play major roles in instigating the action.
Author Lemony Snicket (an assumed name as the author is as much a character in the story as the Baudelaires are) does an excellent job in presenting the story of the Baudelaires experiences at a hospital trying to research in the records room what the truth behind the events of the past several novels and once more running afoul of the minions of Count Olaf and being placed into mortal danger once again. Snicket sets up the next volume very well and tells the story in such a way that the novel flows into the next book while telling an independent story at the same time. The breaking of the formula of the series is a refreshing change and spices up the action quite a bit. The Hostile Hospital is one of the best of the first eight volumes in this series.