I imagine that there is a disclaimer somewhere in The Rosie Project that all characters are fictional, but I actually married Don Tillman. This I know because he even responds to me now when I call him Don. It may possibly be my favorite book ever, but then again, maybe I'm a bit biased?
I'm sad about the movie, because Hollywood can rarely do a great book justice, but I'm happy for your success.
They are indeed all fictional, but you're not the first person to say she married Don. I think some of Don's characteristics are so strong / unusual that when we recognise them in another person we make the identification. People frequently say, "reading the Rosie books is like being in Sheldon Cooper's head" but I've never watched Big Bang Theory. I guess it's like meeting a person from an unfamiliar culture - and then recognising that you already know someone '"like that". But as you dig deeper, you see the individual differences. That said, I've had couples say that reading the books together helped them communicate. "Do you think like that?" "Of course." But of course that's not the sum of the person.