Agreeing with your main point: Apple does not provide a great solution for ebook library management and sync to iOS. But there are good third-party options. I

Agreeing with your main point: Apple does not provide a great solution for ebook library management and sync to iOS. But there are good third-party options. I recommend Kybook 3 on iOS for ebooks. OPDS sync from Calibre works well. I only have occasional use for an iOS CBR/CBZ reader, but ComicFlow has worked for me, without any memorable problems.