While Inkheart happens in our world and can stand alone as a complete story, Inkspell and Inkdeath both happen in the magical realm of Inkworld and are written as one continous story. Funke's Inkworld is a richly imagined world comparable to Hogwarts. It has everything from spirits, giants, glass men, brownies, faeries, shapeshifters, and giant nest trees, to old mysterious castles that are all a treat to the imagination.
Characters. The leading characters are strong and well-built. However, there are too many side characters and creatures that can make the story a little hard to follow. But if you have made it all the way to the third book you would probably have gotten used to it by now. Perhaps this was Funke's attempt at making Inkworld as real as possible by filling it with all these magical creatures and places.
Plot. Just like the first two books Inkdeath didn't have a strong linear plot that slowly builds up to a climax. Instead it has a long and winding one, and it took me a lot of patience to finish this thick, almost 700-page, book. There were several unnecessary scenes and events that only lengthened but didn't add to or build up the plot (such as Mortola's unsuccessful attempt to kill the Black Prince w berries, and Mo's transfer to the Castle in the Lake after he gives himself up to Violante because everything after that could have just happened in Ombra and there would not have been a big difference to the story.)
As a narrative for me the book fails completely, just like the previous books. Events happen and end abruptly without proper build up or transition even if they are crucial. Characters suddenly speak even before they're properly set up in the scene. It was a little difficult to follow at times. Perhaps it was 'lost in translation' from the original German?
Values. As a children's book I would think twice before giving Inkdeath to a 10-year-old. It has more violence than expected including numerous sword slayings, flaying of a man alive, dismemberment, etc. This to me makes it more fitting for young adults.
Mortimer's role as a father is central to the story but children may misunderstand that when he was being selfish and not thinking about his family he was actually under the Bluejay spell. Resa's role as a mother entailed a lot of sacrifice on her part to save her family but was not properly appreciated nor acknowledged, especially by Meggie who remained distant from her until the end of the story.
All in all, Inkdeath can be an entertaining read as long as you don't mind the long winding plot. 3.5 stars.