Originally Posted by
Jackson Richardson
I don't think strictly speaking The Woman in White is epistolary, ie written in letters. It is a series of memoirs by different narrators, collected after the events.
Evelina by Fanny Burney is in letters (I haven't read it) as is Jane Austen's early Lady Susan.
I thought Humphrey Clinker was sweet and I'm sorry I'd forgotten it. As I remember, the letters are from a wider range of personalities than in Pamela or Clarissa - for all its length, there are only four significant correspondents in Clarissa - Clarissa, Lovelace and their confidantes.