Fixed-layout ebooks are a lot like PDFs: everything has to have a fixed place. They are designed with a specific device in mind and don't display well on all devices.
A fixed layout might be necessary for textbooks, but is a no-go for fiction. Amazon only accepts fixed-layout ebooks in the following categories: reference books, comic books, and children's books.
Barnes and Noble only accept fixed layout ebooks if they are children's books.
The following stores accept fixed layout ebooks: Amazon (special terms: mentioned above), Apple, Google, Scribd, OverDrive, CNPIEC, Dangdang, Gardners, Mackin, Bibliotheca, E-sentral, Hungarian stores (Ekonyv.hu, Multimédiapláza, E-letöltés).
The following stores do not accept fixed layout ebooks: 24Symbols, Barnes and Noble (except for children's books), Bookmate, Bookshout, Ciando, Dibook, Dreame, Hoopla, Kobo, Odilo, Perlego.