Book vs Film: What Did the Adaptation Change?

You read the book, watched the adaptation, and spent the whole film mentally noting what they cut. This lays it out properly: the plot and structure changes with the likely reasons, the characters merged or dropped and whether that helped or hurt, the themes amplified or lost, and what the adaptation understood that the book didn't.

I've read {BOOK_TITLE} by {AUTHOR} and watched the {ADAPTATION_YEAR} film/series adaptation. Give me a structured comparison of the two. Cover: (1) major plot or structural changes and the likely reasons behind each, (2) characters who were altered, merged, or cut, and whether those decisions weakened or strengthened the story, (3) themes that were amplified or lost in translation, and (4) what the adaptation understood about the source material, and what it missed. Finally, give your verdict: does the adaptation stand on its own terms, or does it require the book to make full sense?