If you're an avid reader, you've likely collected a number of series over the years. And whether you're a Harry Potter aficionado or an Outlander fan, chances are those books you've been keeping on a shelf somewhere in your house are just collecting dust.
Luckily, if those books aren't being used, a few of those series could fetch a good sum of money on eBay today. We took a peek through the site to see which series are going for the most cash -- and you may be surprised by how much money you could get for them. (One series' asking price is $11K!)