The Prophet, Kahlil Gibran
The Anne Shirley Books (yes all 8 of them), Lucy Maud Montgomery
The Robber Bride, Margaret Atwood
The Pursuit Of Love, Nancy Mitford
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Star Wars novels. Especially the X-Wing saga.
Garrison Keillor’s Lake Wobegon Days. Reading that book is like eating hot biscuits – it’s good for whatever ails you.
I hate the SOB, and would never buy anything new he puts out, because god knows he’s a miserable hack of a writer, but The Belgariad, by David Eddings, is wonderful comfort reading.
Mary Stewart - The Crystal Cave, The Hollow Hills and The Last Enchantment
Anne McCaffrey - Dragonriders of Pern (the first 3 and a couple others but none of the new crap by her son) or the Killashandra or Talents series
Sharon Shinn - any of her Samaria series
David Eddings - The Redemption of Althalus or The Belgariad
Mercedes Lackey/Andre Norton - Elvenbane
Mark Twain - A Conneticut Yankee in King Arthur’s Court, Personal Recollections of Joan of Arc
Fairy tales, of any stripe. I’ve got a few different collections and legends either traditional (blood and guts), Disneyfied, politically correct or adult. Always a nice wuick read.
All these have a place on my bookshelf, and when I don’t feel like reading anything new on my library pile I generally grab one of these.
I read the Dragon singers
I re-read compulsively. My current favourites for comfort are:
Lynn Flewelling’s Hidden Warrior trilogy
Most of the Miss Read books about Fairacre (nothing ever happens! They eat sponge cake! It’s great!)
The second half of Diana Gabaldon’s Outlander series
All the pretty crummy Recluce books
Sunshine, by Robin McKinley
Thought of another:
Good Morning, Miss Dove, by Frances Gray Patton.
Catcher in the Rye. I’ve read it about ten times.
Anything by Salinger, really. It sounds horrible, but I can’t wait for him to die, so we can finally read all the stuff he’s been writing for the last fifty years or so. Unless it ends up being about a million pages of super-philosophical Buddhist nonsense. Then I’d be really disappointed.
I also read Heinlein for “comfort”. Isaac Asimov, too.
Any of the Travis Mcgee novels by John D. McDonald.
I have three. The Hitchhiker’s Guide to the Galaxy, The Hobbit, and A Midsummer Night’s Dream.
I have others that I love and have read many times. But these three are my go to books when I just want to snuggle down and relax.
Dragon Singers are among the few others. 
As is The Masterharper of Pern.
Little Woman the classic adolescent novel.
I have to echo any one of the Hitchhiker’s novels. I have a hard cover book with all five novels, plus a short story called “Young Zaphod Plays It Safe.”
Any good Star Trek novel.
Any Spenser novel.
Anything by Elmore Leonard.
Anything by Evan Hunter or his alter-ego Ed McBain, particularly the 87th Precinct novels written under McBain.
I’ve lost count of how many times I have reread William Goldman’s The Princess Bride. Ah, if only I could get hold of the original S. Morgenstern version. 
Children’s books. Top choices: the Little House books by Laura Ingalls Wilder, the Betsy-Tacy books by Maud Hart Lovelace, anything by Beverly Cleary.
If I’m feeling moody I will sometimes pick up an old favorite book and skim through it, looking for my favorite scenes. Diana Gabaldon’s *Outlander *series is good for this (I can look for all the Lord John Grey bits, for instance.)
Like others here, I’ve read Gone With the Wind several times. Also James Herriot’s All Creatures Great and Small books, the original *Pern *trilogy, Dune, and Heinlein’s Friday.
Lissla Lissar, I only discovered *Sunshine *last year, and I’ve read it three times already.
Dave Barry books
The New Annotated Sherlock Holmes
The Day of the Jackal by Frederick Forsyth
Random Heinlein writings
Dave Lileks’ Gallery of Regrettable Food and Interior Desecration
Weller’s **Science Made Stupid ** and CVLTVRE Made Stupid
Wodehouse – especially the Jeeves stories.
I also like Tim Dorsey’s novels a lot. Anarchy and violence with a brain.