My books are my babies. I can imagine myself stuffing all of my books in a dufflebag. But since that is not plausible as nobody could physically carry over 200 books, I guess I'd settle for these:
My Harry Potter Series
Because even as a child, these books brought me happiness when nothing else could.
My Lord of the Rings Trilogy (Including The Hobbit)
Who doesn't want to share an adventure with Gandalf and the dwarves and help save Middle earth?
Warriors: The Original Series
I grew up reading these. Running through the woods with Firepaw until he became Fireheart and his friend Greystripe. Loved those books, tear jerkers though.
Facts the will scare the s#it out of you
'A rat can compress its body to fit through an opening as small as a half a diameter, making it almost impossible to rat proof a building or a home. I once compressed a rat smaller than that-with a shovel.'
Grey's Anatomy
In case I need it as a reference
Merck Manual
A disease reference, very handy
Lexicon of psychiatry, neurology, and neurosciences
Don't want to lose my wits