Hardy was born in 1840; Woolf, in 1882. In 1915, she had written only one novel and many, many reviews. So, she approaches him very much as a young writer approaching an elder. The letter is brief and gracious: she has a clear pretext (Satires of Circumstance  includes a poem to her father, Leslie Stephen [1832-1904]), but it’s the last line that I love:
I write only to satisfy a very old desire, and not to trouble you to reply.So graceful and grateful. That’s a real fan letter.