The Hostile Hospital (book 8 of 13) is the first volume (I believe) to introduce the idea that the children themselves have to do things to survive that, while understandable, are not 'noble' when viewed in isolation. This begins in earnest the theme of noble vs villainous people that dominates to the end of the series. 
 It demonstrates an increasing sophistication in the novels, perhaps born of the idea that the audience were growing older over the years that the books were published. 
 In previous books we've often had a guardian who whilst well intentioned (though often deeply stupid) lacks the moral fibre to act when doing the right thing requires some bravery. In this book, and those remaining, it is the children whose actions are slowly called into doubt. 
 This path begins very gently in this book with the necessity of the children lying to &/or tricking various people in order to preserve themselves. Additionally the children begin to adopt the tactics of their enemy - using disguises themselves. 
 Guardians who refuse to recognise Count Olaaf are a thing of the past and instead we are drawn deeper into the mystery of VFD and the events leading to this current series of unfortunate events. 
 Our 3 heroes continue to suffer and are put in great jeopardy by Count Olaaf and his crew. The ending also departs from the pattern - Count Olaaf does flee the scene ... but there's a crucial difference this time. 
 Celyn enjoyed this one as she has enjoyed the previous volumes. Some of the wordplay goes over her head ... but then it's entirely possible that some of it goes over mine too. 
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