Hi Simon – You can create any number of wordpress pages – and use them as the front page or add them to your menu using the CBOX theme. You don’t need to use our homepage template. You don’t even need to use the CBOX theme, if you don’t want to use its design. You can make any page password protected, too – though that option is a little clunky.
If you choose to stick with our theme – you might need to install a page builder plugin to help you design something like the Wisteria site you linked to.
But the issue seems to be that you want only members to be able to access your library. I still think a private group would suit your needs. If the un-logged on or unregistered user tries to access the link on your front page – they are challenged for their credentials.
You also have the option to make the entire site only open to registered users – but it does not seem to be what you need.