Reflowable
Advantages:
Ideal for books, novels, and guides.
Easy to read on smartphones, tablets, and eReaders.
Adapts to the reader’s preferences (font size, night mode, etc.).
Disadvantages:
Does not preserve the exact layout of the original document.
Difficult for books with complex layouts, such as magazines, educational manuals, or comics.

Fixed-Layout
The page layout is fixed and remains the same on every device, similar to a PDF.
Advantages:
Ideal for children’s books, comics, illustrated books, and educational books with tables/diagrams.
Images and text stay in the same position as in the original design.
Disadvantages:
Harder to read on small screens (e.g., smartphones) because the text does not reflow.
Larger file sizes.