However, being the logical person that I am, I decided to do a little of my own research before I totally freaked over it. :D I think some of you might feel as relieved as I did, seeing what I found:
Richard Adams: Watership Down at 52.
Lloyd Alexander: the Prydain books, from 40 to 44, Westmark at 57.
Natalie Babbitt: Tuck Everlasting at 43.
Arthur C. Clarke: A Fall of Moondust at 44, 2001: A Space Odyssey at 51.
Beverly Cleary: the Ramona books starting at 39, The Mouse and the Motorcycle at 49, Dear Mr. Henshaw at 67.
Roald Dahl: Charlie and the Chocolate Factory at 48, The BFG at 66, The Witches at 67, Matilda at 72.
Peter Dickinson: Eva at 61, The Kin at 72.
Edward Eager: the Magic books (all he wrote) from 43 to 51.
Michael Ende: The Neverending Story at 47.
William Golding: Lord of the Flies at 43, Darkness Visible at 68.
Robert Heinlein: Starship Troopers at 52, Stranger in a Strange Land at 54, The Moon is a Harsh Mistress at 59.
Hemingway: published a couple of his major works in his twenties, but then there's For Whom The Bell Tolls (at 41) and The Old Man and the Sea (at 51).
Eva Ibbotson: Which Witch at 54, The Secret of Platform 13 at 69.
Diana Wynne Jones: the Chrestomanci series from 43 to 54, Fire and Hemlock at 50, Howl's Moving Castle at 52.
Ursula LeGuin: Earthsea Trilogy from 39 to 43, The Left Hand of Darkness at 40, The Lathe of Heaven at 42, Tehanu at 61
Madeleine L'Engle: A Wrinkle in Time at 44, A Wind in the Door at 55, A Swiftly Tilting Planet at 60.
Elmore Leonard: La Brava at 58, Get Shorty at 65, Out of Sight at 71.
C.S. Lewis: Screwtape Letters at 43, the Narnia books from 52 to 58.
Anne McCaffrey: the Pern series from 42 to 70 or so.
Vladimir Nabokov: Lolita at 56, Pale Fire at 63.
George Orwell: Animal Farm at 42, 1984 at 46.
Terry Pratchet: started Discworld series at 35 (still continuing; he's currently 59), Good Omens at 44, The Wee Free Men at 57.
Philip Pullman: the His Dark Materials series from 49 to 53.
Shel Silverstein: Where the Sidewalk Ends at 42.
Zilpha Keatley Snyder: The Egypt Game at 40, The Changeling at 43, The Headless Cupid at 45, The Truth About Stone Hollow at 47, A Fabulous Creature at 55.
Tolkien: The Hobbit at 45, The Lord of the Rings, written over the course of 16 years (age 46-62, approx.).
Vivian Vande Velde: Dragon's Bait at 41, Heir Apparent at 51.
Cynthia Voight: Dicey's Song at 40, On Fortune's Wheel at 48.
Kurt Vonnegut: Mother Night at 40, Cat's Cradle at 41, Slaughterhouse-Five at 49, Breakfast of Champions at 53.
E. B. White: Stuart Little at 46, Charlotte's Web at 53, The Trumpet of the Swan at 71.
Connie Willis: Domesday Book at 47, To Say Nothing Of The Dog at 52.
John Wyndham: The Chrysalids at 52, The Midwich Cuckoos at 54.
Jane Yolen: Dragon's Blood at 43, The Devil's Arithmetic at 49, Briar Rose at 53.
Maybe it's just me, but somehow it's a relief to know that even if I'm 60 by the time my first book is coming out, it could still be damn good.
And because I did promise kitty pics...
"Can we pleeeease go out on the balcony, Mom?"
Kitty chair kung-fu.
Everyone's favourite chair.