(Probably Found) Need Help!

[BMK!]

I'm looking for the name of a book. I believe it was the first in a series. All I remember is that the cover had a boy looking into a portal underneath tree roots with some giant spider-like thing with him. I got this book used in a book store so it might be from the 70s-80s. Can anyone identify this book?

Thanks!

-BMK!-

 

[Tequila]

You don't happen to mean the Spiderwick Chronicles? Your description reminds me of that series.