What struck me reading this piece was how little like a letter it really is. When one writes a letter, one writes to an individual, and mostly keeps that individual in mind. The paragraphs fill the individual on this or that, and often, at least in my experience, are riveted on a tiny timeframe of a group of events which one's interlocutor shares. For comparison I took Lettre III from Les Liaisons Dangereuses, dated Paris ce 4 aout 17__. It's fastened on the interlocutor and a timeframe; it's not a chunk of first person dramatic narrative, which is what this extraordinarily brilliant series of dramatized pictures is.
Why did Richardson choose to divide up his first person narratives into letters then? Lots of reasons: different voices interplaying, different perspectives, &c. But there are two that struck me in this letter: i.e., Clary doesn't know how it's going to end for her, and it's all in an agonized present tense (going on in front of our eyes right now). Will she be forced to marry Solmes? Will she go to the dreaded cottage (I see that as a more early Gothic motif than a hint of incest)? What will happen in the next minute? Will papa hit her or her mother?
Richardson himself suggested the creation of intense suspense and the versimilitude of present-tense dramatic narrative as his two reasons for using epistolary narration in his preface when he said:
All the letters are written while the hearts of the writers are supposed to be wholly engaged in their subjects (the events at the time generally dubious) so that they abound not only with critical situations, but with what may be called instantaneous descriptions and relfections ... 'Much more lively and affecting,' says one of the principal characters, 'must be the style of those who write in the height of a present distress, the mind torutred by the pangs of uncertainty (the events hidden in the womb of fate) than the dry, narrative, unanimated style of a person relating difficulties and dangers surounded can be ...
As to the content I was struck by the physical threats implied throughout. This motif connects both Clarissa and her mother (who is not only physically but morally timid). It is Clarissa's physical timidity that her relatives here, later her father, and much later Lovelace all take advantage of. I have wondered if we are to connect Clarissa's real reluctance for any physical contact with Lovelace to this physical hesitance she has (she is never willing to carry anything very far; flinches so quickly)--it blackens the eventual rape, as well as heightening the ugly bullying to which her brother subjects her, and which everyone seems to know about: the father raises his voice to make her nervous; Uncle Anthony who never keeps the higher ground (doesn't seem to know there is one) immediately acts "in his rougher manner" and so on.