This was a very, very entertaining book about a twin brother and sister who go to live on their grandfather's nature preserve. But when they get there, they realize there are many odd rules, such as you must lock the shutters at night, you can't wander to far into the woods, and stay away from any wildlife. When the brother disobeys one of these bizarre rules, the twins find out they were there for a reason: There are mythical creatures at this nature preserve. Why? Because it is Fablehaven, a safe haven for any magical beasts pushed out of society by humans. 

This was a rather quick read, and the rest of the series was just as good as the original book. These books tend to end up at thrift stores often, and most of the time for just fifty cents. So you don't need to spend yur entire allowance at Barnes & Nobles for a Fablehaven book: You can just go out to a Goodwill. You can also find Fablehaven at most local libraries, because it is such a popular series. I'm sure one of your friends probably has it, too, so you can always borrow it from them.