Is it normal to be still reading children's fantasy books in 27?

Don't let your girlfriend dictate what you do. The things we like makes us who we are and she shouldn't try to change you or force you to give up something you love.

40 year olds read Harry potter.......

Your girlfriend shouldn't tell u what to do. It's not like it's a harmful pastime. Kick her to the curb if she'd going to lay down rules like that!!!

It is totally normal. I still read biff and chip and tug myself off.

I get this all the time, because I engage in many behaviors typically only displayed by children. Such as:
1) I read children's books, and not only classics. I keep up with new releases in child/teen fiction and ask my ten- to thirteen-year-old cousins for book recommendations.
2) I blow bubbles in my chocolate milk.
3) I love playgrounds. They should make them for adults.
4) I minorly freak out when I see a dog or cat and have to ask the owner if I can pet it. I also stop the car when I'm driving to pet horses, cows, goats, etc, through the fence (I live in Wyoming, so there's a lot of livestock).
5) I love kids' movies. I just saw Disney's Frozen in the theater and I found it to be a moving, relatable, and emotionally significant film.
6) I usually have candy somewhere on my person. Hershey's kisses in my pockets, peppermint patties in my purse, Starbursts in my backpack. You get the picture.
I think the important distinction with these kinds of things is to be childLIKE, and not childISH.

Childlike: being open to new things and people, taking delight in the small things, maintaining a sense of wonder and fascination with the incredible world around us - including children's books, nature, bubbles in milk, enthusiatically petting animals, etc.
Childish: pouting, sulking, throwing tantrums, insisting on getting your way, etc.

I would explain to your girlfriend that reading children's books makes you happy and keeps you in touch with your sense of wonder - or whatever it is about them that floats your boat. It is a childlike behavior, not a childish one.
Read on, brother. If I was your girlfriend we'd be swapping reading lists and watching Lilo & Stitch.

I read Enid Blyton's Book of Brownies when I was 27. Best read of the year. I've sinced moved on to more grownup stuff like Harry Potter. The wordz is dificolt but I gets ther.