I've seen these at the book store for a while but haven't picked one up. Since my son has matured I find I'm not reading as much fantasy. This was a perfect blend of possible and fantastic. The premise is that there are preserves throughout the world in which all the fantastic and magical creatures are kept for their own safety and for the safety of the human residents of the earth. Kendra and Seth end up in Fablehaven because their parents have to attend a funeral/cruise (their maternal grandmother's final bequest to her children--by the way a great idea!).
The grandparents are the guardians of Fablehaven. Their parents do not know of the nature of this preserve. The story is well crafted and an excellent balance of kid adventure and adult mentoring of kids. I strongly recommend the book. Lexile is 700. Recommended for older kids (I agree).