not2easy - 9:00 pm on Jun 12, 2013 (gmt 0)
You should consider the projected sales figures before signing on to the full service cart. For shops with a multitude of products it makes sense to use a complete solution. For shops with a limited inventory, such as an author offering books you need to consider the overhead. If using a "full service" provider is going to land the shopper in PayPal, you might as well work with PayPal's solutions to start with. They do have better tools these days.
Unless this author will have a Merchant Account and a processor account (like Authorize.net or Verisign) and doesn't mind considerable overhead whether there are sales or not, they could be very unhappy.