Believe it or not, there are many kinds of blurbs.
Blurbs can fall into the categories of: summary, historical, informative, literary and biographical. And more. This is of course mainly for works of fiction.
If you wished to write a summary blurb for Villette, you might begin as follows.
Having lost her relatives and a job as companion to a rich lady in her neighborhood, Lucy Snowe sets out for the city of Villette (fictional name for Brussels) in the country of LaBasseCoeur (Belgium).
The "Women Question" was being discussed at tables of intellectuals and literati all around England during the years that Charlotte and Emily Bronte made their way to the Pensionnat and Ecole Heger in Brussels, Belgium(1830's-1840's). What, oh what should be done with "surplus" unmarried women? Charlotte Bronte's idea was to acquire certain branches of education that befit the bringing up of a lady, and then to open her own school."
Charlotte Bronte was 37 when Villette was published. It was her last and probably her most realized and mature work. In it she wrestled with and wrought to completion issues which had haunted her since she had left the Ecole Heger in Brussels ten years before.
Jane Eyre is by far the best known of Charlotte Bronte's novels, but Villette is probably the most thoroughly successful and original as a novel.
Both Emily and Charlotte wrote their childhood dreams of dangerously attractive men in their tales of Gondal and Gaaldine. Emily wrote a much more adult version of Gondal in Wuthering Heights, with Healthcliff as the male hero/antihero transformed into an orphan who becomes a landlord and in his way a force of nature. But Monsieur Paul, Charlotte's most realized and complete male character, is both worldly and irresistible, not because of his looks or evil intent, but because of his passion for warmth, truth and, in his own way, love.
As you can see, the five kinds of blurbs I mentioned often blur/blurb into each other. That is the way of blurbs, unless they are strictly summary.