My app is a catalog of ebook-like content. Some of which are free to read, and some other are paid. I need to ask for user email / password to be able to retain the information of which content was successfuly completed, or until which chapter it was completed so the user can have his information synced accross all platforms.
However I got this rejection message :
Apps cannot require user registration prior to allowing access to app content and features that are not associated specifically to the user.
Next Steps
User registration that requires the sharing of personal information must be optional or tied to account-specific functionality.
To resolve this issue, please make it clear to the user that registering will enable them to access the content from any of their iOS devices and provide them a way to register at any time, if they wish to later extend access to additional iOS devices.
Please note that although guideline 3.1.2 of the App Store Review Guidelines requires an app to make subscription content available to all the iOS devices owned by a single user, it is not appropriate to force user registration to meet this requirement; such user registration must be made optional.
Please resolve 5.1.1 issue and resubmit your revised binary to iTunes Connect.
I am very surprised as I know apps such as Feedly which do not allow you to subscribe to RSS feed unless you create an account.
How should I get this problem solved ?
I have faced the similar rejection. As per the guide lines app is not supposed to force registration. So I ended up adding a skip button on the registration page. You need to add some content that users can view without registration. For example a user can preview a FREE book (maybe first page only) but can't read the full book without registration.
You can keep asking user for registration later when user is browsing the content.
There are some apps with forced registration and are available in AppStore like WhatsApp. But you need very strong arguments to convince Apple review team to consider and it's only possible if your app is really can't work without registration. In your case I don't think that's true.
For registration and login, your app must Serve contents/data user wise. e.g. Specific user settings, profile or follow topics etc. If your app does such things then Apple wont have any problems for your login or registration.
This is because of some apps have Registrations just to collect the email addresses of users.
If i will add "Guide" screen, then this issue will be resolved or not!
来源：https://stackoverflow.com/questions/45788841/app-rejected-because-asking-user-registration-guideline-5-1-1