The topic of surge protectors comes up here on a regular basis. There are many opinions, but the fact of the matter is that there is a lot of hype and myth out there, and not much much in the way of real information (start with the fact that the term "surge" is undefined!)
On Saturday mornings, I always read the RVTravel newsletter. This week, their electrical guru has written a really good article on this topic. Besides talking about different kinds of "surges", he describes the devices known as surge protectors and what they can and cannot do (some of it is scary). He also describes the difference between surge protectors and voltage monitors. As you read, remember that although he uses one manufacturer's products as examples, these are not endorsements and there are other manufacturers out there.
I haven't yet received permission to copy this article (and I would de-commercialize it if I did), but it is a good read in its original location. If you have wondered about these things, check it out.
http://rvtravel.com/noshockzone/surge477.shtml
Bill