LOL Dawn, picking a favorite book is a lot like picking a favorite child - I love so many.
Limiting myself to books written for adults, the book I've read the most - which one might say is my favorite - is Pride and Prejudice. I came to it as an adult, so I already knew what it was to be at a cocktail party with a bunch of affected, nervous people putting on a false front. (mind now, not that everyone at cocktail parties does that - but you get the picture). The cleverness with which Jane Austen pricks out each person's weaknesses absolutely sent me over the edge in laughter. Darcy's proposal is a classic piece of hilarity.
And at the same time, I completely understand how a perfectly rational intelligent person can open her mouth and watch black bats and squiggly worms squirm out! I've DONE it!
Since I have read P&P maybe ... what? 40 times? I'd have to claim that as my favorite
then I think about other books I adore ... like
The Little World of Don Camillo by Giovanni Guareschi - where the priest prays just the same way I do and gets the same sort of answers I get
Jane Eyre by Charlotte Bronte - where the essential dilemma of How Do You Choose Between Your Head and Your Heart is worked out to my own complete satisfaction.
Sword and the Swan by Roberta Gellis - who can take the words from the old Scottish folk song Geordie and weave it into the plot of a story. And nobody can write a battle scene as vividly as she does. I like all her novels, especially because she chooses my kind of hero.
Faro's Daughter (or pretty much anything else) by Georgette Heyer - who is the ONLY person who can write a regency romance worthy of following Jane Austen ... who was not writing historical fiction anyway - but contemporary fiction.
Shinju by Laura Rowland - a murder mystery set in the Shogun period of Japanese history but so tightly written you could set it in modern times
Portuguese Irregular Verbs by alexander McCall-Smith - the whole trilogy, actually - I am laughing now just remembering the silliness of it - how Englishmen poke fun of Germans so so funny
Life of Pi by Yann Martel - which I loved so much I will never see the movie - no matter how good it is
Ditto "Schindler's List" by Thomas Kennealy - even though I adore Liam Neeson
some books should remain in our hearts and in our heads
Eye of the Needle by Ken Follett - such a perfect spy novel - so precise, with no plot flaws, perfect pacing, characters to care about - that I didn't read another of his books until he started writing about Cathedrals.
Cry to Heaven by Anne Rice - juicy and erotic but so well written you can't really classify it as erotica. The plot is as true as glass. No flaws and she gives an amazingly accurate depiction of how a classical musician is trained. her descriptions are so vivid you feel yourself in the molding damp world of 17th century Venice.
Well - that is 10 of my top 100 in no particular order and alas, I could go on and on and on forever. This started out as an answer to a question but I decided to turn it into a blog post. Happy Reading to my spark pals