The Collaborative International Dictionary of English v.0.48:

Bookworm \Book"worm`\, n.
   1. (Zool.) Any larva of a beetle or moth, which is injurious
      to books. Many species are known.
      [1913 Webster]

   2. A student closely attached to books or addicted to study;
      a reader without appreciation.
      [1913 Webster]

            I wanted but a black gown and a salary to be as mere
            a bookworm as any there.              --Pope.
      [1913 Webster]

WordNet (r) 3.0 (2006):

bookworm
    n 1: a person who pays more attention to formal rules and book
         learning than they merit [syn: pedant, bookworm,
         scholastic]
    2: someone who spends a great deal of time reading

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "bookworm":
   bibliognost, bibliographer, biblioklept, bibliolater,
   bibliolatrist, bibliomane, bibliomaniac, bibliopegist, bibliophage,
   bibliophile, bibliophilist, bibliopole, bibliopolist, bibliotaph,
   bibliothec, bibliothecaire, bibliothecary, book agent,
   book collector, book printer, book publisher, book salesman,
   book-stealer, bookbinder, bookdealer, booklover, bookmaker,
   bookman, bookseller, cataloger, chief librarian, college editor,
   copy editor, curator, dictionary editor, editor, editor-in-chief,
   executive editor, failing student, greasy grind, grind,
   juvenile editor, librarian, library director, managing editor,
   mugger, overachiever, permissions editor, philobiblist, printer,
   production editor, publisher, reference editor,
   reference librarian, swotter, textbook editor, trade editor,
   underachiever