“Hmm, it looks a bit long. Do you have anything with pictures and less than, say, seven chewable pages?”
To the OP: depending on your co-worker and how thick-skinned she is, you may be able to get some good conversations going by talking with her about why you don’t like the books, or the kinds of books, she recommends, kind of like Nava said. Just don’t use words like “suck” that imply that something that you don’t like is necessarily objectively bad or, worse, that she’s dumb for liking it (even if it’s true).
To CairoCarol: I can understand why some people like that level of description: It may help them to picture a scene, or to more fully get inside a character’s head. I can also understand why some people hate it, especially if those people read relatively slowly or if the author doesn’t do it particularly well.
“Ah, cool—you like rape too!”
Well, you’ve read some of her suggestions, usually when you’ve both read the same books it makes for good discussion. Make sure you have a detailed opinion ready (more than " it is horrible. It’s long, it’s too detailed, it’s boring") and get ready to share your experiences. That way, soon she’ll know what you like. She might say “as you thought GwtDT was too long, here is a haiku” and then you could say: “well, that was rather short” and then she would give you Ulysses and so on. You get to know each other’s likes and dislikes, get better at recommending stuff and also hopefully some interesting discussion (as you don’t agree).
For what it’s worth (I suspect not too much) I’m in the process of reading aloud to my wife the Millennium Trilogy that includes your example sucky book. I’m not here to defend the book as such, since I came at the story first by watching a Netflix streaming version of it (the original Swedish version) and the two follow-up stories right after that.
Larsson obviously enjoyed Ian Fleming’s way of getting at character and setting by using intricate detail to do so but there’s also a touch of Hemingway in the short declarative sentences. It’s easy to read aloud.
I’m enjoying the stories (we’re on Volume II now) a good deal. Taste, I guess you could say. Or lack of it. 
As for your concerns about how to alert the co-worker that your tastes don’t jibe, offer to share some of your choices with her.
For an even more difficult dance than the one posed in the OP, try telling a co-worker that his books suck, when he’s the one who wrote them. :eek:
Actually the one he lent me (for a review) that I was able to get through wasn’t bad, except for needing major editing for grammar and fluidity. I was encouraging.
“I think we have different tastes. Here, try this one, or this one, and tell me if you like books like these.”
She’s hitting on you. Next time she offers you a book just say, “Let’s cut to the chase, sweetheart. How about we meet in the supply closet in ten minutes and I’ll give you the kind of screwing you’ve only read about!”.
That ought to do it.
Letting her think that you enjoy her books is the same as if she had bad breath. The longer you take before you tell her, the more embarrassing it becomes.
Wear a t-shirt to work that reads:
I don’t eat tripe.
I don’t read it, either.
I agree with Napier. “I think we have different tastes.” is honest and lets your co-worker face-savingly conclude that it’s your taste that’s deficient (there’s no need to insist otherwise).