I know Amazon assigns one to your book when you upload it, but do I need one for B&N, Kobo, and iTunes?
No. B&N provides an ISBN for ebooks as well as print books you publish through them. Kobo provides an ISBN for ebooks. (They don't do print.) I go to iTunes through Draft2Digital and they provide an ISBN for that. So not 100% positive for if you go direct with them but I don't believe you need one there either.I know Amazon assigns one to your book when you upload it, but do I need one for B&N, Kobo, and iTunes?
No. B&N provides an ISBN for ebooks as well as print books you publish through them. Kobo provides an ISBN for ebooks. (They don't do print.) I go to iTunes through Draft2Digital and they provide an ISBN for that. So not 100% positive for if you go direct with them but I don't believe you need one there either.
D2D does distribute to Apple Books.
It is to your benefit to know about ISBN requirements, notwithstanding any free offerings from publishers/distributors/etc. These sites may help . . .
https://www.isbn-international.org/content/guidelines-assignment-e-books
https://www.myidentifiers.com/get-your-isbn-now
Yeah just go through D2D, then you will be covered. One ISBN, free, and it works for all the sales channels you choose to port to.
No, no. I know they do. I was asking about iTunes because I didn't see it on the list.
From what I can tell from online info you can buy books through both the iTunes app and the Apple Books app, but the book comes from publisher Apple Books as AW Admin says.
https://www.apple.com/apple-books/
https://books.apple.com/us/genre/books/id38
The difference seems to be that thru Apple Books app you get only books, thru ITunes app you can get books and music and video and etc.