I'm listing these in alphabetical order by last name because for some of them I don't have an exact count on how many of their books I've read.
I've read her six major novels, plus some of her juvenilia, Lady Susan and what there is of The Watsons and Sanditon. My favorites are Persuasion, Pride and Prejudice, and Northanger Abbey. I like Austen for her caustic wit, shrewd observations of human nature, and fully realized characters.
Chandler is my absolute favorite author, so it's no surprise I've read all 7 1/2 of his novels (the 1/2 is cuz he never completed Poodle Springs, but Robert B. Parker did an entertaining job finishing it) and many of his short stories and essays. I don't exactly have a favorite of his books, though I'm very fond of The Big Sleep, The Lady in the Lake, and Farewell, My Lovely. I like Chandler for his surprising descriptions, acerbic dialog, and brisk pacing.
A. Conan Doyle
Of course by now you know I'm a devoted Sherlockian. I read the entire canon in 12 months not long ago, but I'd read nearly all of it many times before. I've also read The White Company, which is the only non-Holmes book of Doyle's I've read so far. My favorite Holmes adventure is The Hound of the Baskervilles, and I also dearly love "The Adventure of the Blue Carbuncle" and "The Adventure of the Speckled Band" and many of the other short stories. I like Doyle for creating the coolest detective and chronicler ever and for his inscrutable but logical plots.
I almost didn't put Hemingway on here, but then I counted up how many of his books I've read and realized that I've read 6 1/2 of his books (Garden of Eden is unfinished) and all of his short stories, plus a good many of his essays and articles, so he belongs firmly on this list. My favorites of his are The Sun Also Rises and A Moveable Feast, and I'm quite fond of his Nick Adams stories too. I like Hemingway for his terseness, his attention to detail, and his ability to make me understand characters who are very different from me.
Reading Karon's books about Mitford is a little like making a visit home for me. Why? Because she set Mitford in the mountains of North Carolina and patterned parts of it after the town of Blowing Rock. My family moved to NC's foothills when I was 12, and Blowing Rock quickly became one of our favorite places to visit, so much so that when Cowboy and I got married, we honeymooned there. I haven't read the last few of her books, though I own all of them and look forward to beginning the series over again one of these days. I've read the first six or seven, and am very fond of them. I like Karon for her warm humor, quirky characters, and heartwarming storytelling.
Laurie R. King
I've read all of King's novels of suspense featuring Mary Russell and Sherlock Holmes (my favorite is The Beekeeper's Apprentice), all of her Kate Martinelli mysteries (my favorite is To Play the Fool), several of her stand-alone novels (my favorite is Keeping Watch), and the first of her Stuyvesant & Grey books. In fact, there are only 2 of her published novels I haven't read yet, and I'm kind of holding off on them so I have something to look forward to, other than her upcoming releases. I like King for her strong female characters, exciting mysteries, and especially for her excellent characterization of Sherlock Holmes.
L. M. Montgomery
I've read all 8 of her Anne of Green Gables books numerous times, her Emily of New Moon series, and I'm currently reading a bunch of her short stories. My favorites are Anne of Green Gables and Anne of Windy Poplars. I like Montgomery for her happy endings, fanciful characters, and beautiful descriptions.
I have read all 20 of Patrick O'Brian's novels about Jack Aubrey and Stephen Maturin's adventures in the Royal Navy during the Napoleonic Wars. I also have his unfinished 21st book in the series, but I'm kind of saving it for when I reread the whole series. I like O'Brian for the way he immerses me in a world I would otherwise never visit, and for the complex and endearing characters he created.
I have, of course, read all the Harry Potter books. And the book of stories by Beedle the Bard. My favorite is Harry Potter and the Prisoner of Azkaban, hands-down. I like Rowling for her deft wordplay, humorous dialog, and ability to communicate hard truths simply and kindly.
I'm not even sure how many I have read of Stout's mysteries featuring Nero Wolfe and Archie Goodwin. I know I've read 16 of the books I own, plus probably 6 or 8 more from the library over the years. I've also read a couple of his non-Nero Wolfe mysteries, which were nice, but it's the characters of Archie and Nero that keep me coming back for more. I like Stout for his snappy dialog, twisty mysteries, and memorable characters.