A little research showed that William Makepeace Thackeray's book was titled Vanity Fair: A Novel Without a Hero. This was one of his most famous works.
I could not find an 1848 copy but a bookseller, Yesterday's Muse had this to say about book (they only had a 1936 copy).
"Vanity Fair: A Novel Without a Hero is a novel by William Makepeace Thackeray that satirizes society in early 19th-century England. Like many novels of the time, Vanity Fair was published as a serial before being sold in book form; it was printed in 20 monthly parts between January 1847 and July 1848."
The book may be valuable if the pages, spine and board are intact and soiling, staining, etc. is not too excessive. You would really need to take it to a rare book dealer or send him/her pictures and a detailed description.
