I am a voracious reader, which lends itself well to my other hobby as a writer. I can see what other authors have done with a certain topic, and adapt accordingly. Sometimes I read the bestsellers. Sometimes I read more obscure works. Working at a library helps me with both.
My point is, I don't always follow the literary trends. Yes, I picked up Harry Potter to see what the hype was, and thereafter devoured the entire series and all eight movies. I also picked up Twilight to see what the hype was, and have never touched a Stephenie Meyer book since, even though the rest of the series remained wildly popular. I don't plan on reading the equally-popular Fifty Shades of Gray because, no matter how many people have read and enjoyed it, I've read small snippets and found it to be apocalyptically bad writing.
Reading books because they're popular isn't always a bad thing. A lot of times, they're popular because they have something to recommend them, like a compelling story and engaging characters.But reading books just because everyone else is reading them is not necessarily the best way to gain new reading material. I know people who have read every single book that Oprah Winfrey has recommended. Those titles don't interest me. I know people who would plow through the New York Times bestsellers list if they had the time and money. Some of those titles i may check out, or I may not.
The problem comes when a certain genre of book becomes popular, and writer (like me) try to cash in on the popularity. You crank out a book, polish it, and send it to a publisher--maybe even the same publisher that put out Popular Series--certain that the trendiness of y our book with develop into sales. Then you discover the harsh truth: In the time it took you to write your book, the trend has passed you by. What was popular, isn't anymore. Or worse, your contribution is only the latest in an already oversaturated market, and editors are sick to death of hearing about this topic.
What happens when the trend you were following so faithfully dries up and blows away? How do you find the Next Big Thing? You look at what's just become popular this time around, and decided whether it's for you or not.
Or, you can just do what I do, and take each book on their own individual merits rather than because they're trendy.