I was an English Lit major at college, and I'm pretty picky about books. If I start reading something I don't like, I tend to drop it because life's too short and there are plenty of other books I'd like to read before I die.
This is exactly my philosophy. If it doesn't grab me in three chapters, I pick up something else.
And I agree with the Dan Brown dislikers... I just couldn't get through DaVinci Code. I bought it at an airport to read on a plane when it first came out and I couldn't get through the first chapter. It was written in such an.. illogical way. I can't explain it, it just felt like he kept thinking "oh wait! I forgot to mention this, which was referenced a couple pages ago, but instead of editing it there, I just added it in extra over here!"
Modified to add:
I totally forgot to throw in my pick:
The Historian by Elizabeth Kostova
The book is okay until you get about halfway in. Then it just drones on for 100+ pages with the most boring drabble I have ever experienced. It was so bad that I went on Amazon to find out if anyone else had experienced this, and lots of the reviewers said "skip such and such pages and just go to the end" or they even said "if you want to know the ending so you don't have to put yourself through the misery, here's a spoiler."
I tried, I really did. I ended up reading the spoiler and giving up, and once I read the spoiler, I was annoyed that the ending was so predictable!
I worked at B&N when it first came out and it was super popular. I was just in a Borders two days ago and it was on the bargain rack for $4.98.