Hurtigruten is a voyage along Norway's jagged coastline. This voyage is sometime called the world's most beautiful voyage. Originally, Hurtigruten was used as a means of transportation for passengers along the coast. And for transportation of goods, and mail. The ship still transport cargo. But the ships are bigger today, and resemble cruise ships.
The voyage is a simple way of combining lodging, eating, and transportation in one 6 to 12 day voyage (port stops might be somewhat brief unless one purchases and off-on ticket) which contrasts to Norway-in-a-Nutshell tours (2-3 days).
A museum, including parts and one whole, prior versions of the ship Finnmarken, sits in one port which explains the history of the line.
The price for a full round-trip would be like the price for a ordinary cruise. However it is possible to join the voyage only for part of the voyage. The cost for a such voyage is calculated partly for the distances traveled, and for the cabins. If you would like to cut the cost. This can therefore be done by only traveling during daytime, or stay onboard only one night. Most ships are capable of carrying cars (typically 40-50, excepting the 2 oldest ships). This could make possibilities for interesting round-trip.
Sea-sickness: yes, it is possible. A number of reaches are exposed to the full force of the Atlantic. During winter, there is no assurance that any of the ferries will make it all the way to Kirkenes.
Hurtigruten call these ports, listed from south to north:
Drive back in a car. A full roundrip Bergen-Bergn with ship one way, driving one way, would require two weeks.