Fablehaven

 the fourth book of Fablehaven.

I was reading a series of books that was very interesting called Fablehaven. It is talking about a sister and brother finding about magical preserves, creatures and prisons. It was all thanks to a parent-no kids vacation. Being left at their grandpa and grandma Sorensons. Special milk from a special cow had changed their lives. Friends being enemies, the demise of few and special abilities that are very rare.