As a friend pointed out, this isn't terribly surprising, as the people who write books tend to also like books, and people often write characters who are like themselves.
Unfortunately, some of these book-loving characters just make me roll my eyes.
Since I don't generally object to people liking books, I started trying to figure out why I object to some book-lovin' characters and not others, and here it is:
Your character's love of books needs to tell me more about your character than just that they love books. Just loving books is not enough. Sure, your MC likes books. So does mine. So did the MCs of the last 5 books I read. So does pretty much everybody I know in real life. "Likes books" does not distinguish your character from my mother or next door neighbor. It is simply not enough.
Which books does your MC like? Do they desperately devour anything they can get their hands on, including moldy books they dug out of the garbage? Do they only read Christian Inspiration? Or do they prefer Enlightenment philosophers? Do they absolutely hate something they had to read for school? Or perhaps there is just one book that means a lot to them, like a dog-eared copy of "Are you there, God? It's me, Margaret."
At the very least, the books your character reads should match the character you're describing. For example, if you are writing a contemporary novel with a teenage MC who really likes books, then I expect your MC to read a lot of contemporary YA--books like Harry Potter, The Hunger Games, Twilight, etc. If your teenage MC doesn't like YA, that in itself says something about their personality.
I recently read a contemp in which the teenage MC supposedly liked books, but the only book she actually liked was a "classic" adult novel. The effect felt forced; my suspension of disbelief was broken. I can believe that a teen who voraciously read anything she got he hands on would also like many classics. I'm not going to believe that a teenager who is depicted as interested in only one book in the entire novel is the kind of teenager who would love classic literature.
Rather, the whole business felt like the author attempting to say, "Look, my character is so smart! She loves books!" and then just picking whatever book the teenager might reasonably have encountered for her to love, because obviously a book-loving person will love every book that comes their way.
Let me tell you a little secret about really smart people who like books: they tend to hate a lot of books.
When you're a voracious reader, you develop tastes. And you encounter things you absolutely hate.
For example, I hated Paradise Lost. Personally, I'd much rather read Homer than Milton. That's just me; you're of course allowed to hate Homer and love Milton. I also hated Hawthorne; my husband liked Hawthorne. Oh well.
The character who just loves whatever book they happen to come across feels shallow and incomplete. It sets them apart from the sorts of people who don't like books, yes, but is that really your chief concern?
Let the character's choice in books mean something.