Pamela is one of those books that always has to appear on undergraduate courses on the history of the novel because it was so influential but it is undoubtedly a book which hasn't stood the tests of time well and which is a difficult book for us to read today. Told in epistolary form, it tells the story of Pamela, a servant girl, pursued obsessively by her master who hides in cupboards, gropes her and rapes her until they finally get married...!
So, ok, the story itself might be pretty offensive to us today and the method of telling is frequently repetitive, but it does tell us quite a lot about the culture, gender relations, and role of literature of the time in which it was written. Realism wasn't necessarily what Richardson was aiming for, and neither is the sort of psychological dimension which appears in the C19th alongside the growth of scientific pyschology.
So this is very much a book which you have to take on its own terms - it certainly won't be for everyone but does have a strange kind of vitality and energy of its own.