I try to tread the fine line between simply recounting the plot and giving away all the secrets, and talking about it in ellipses so as to preserve the mystery.
The sort of things I give away are the things you read in the blurb. Circus, love story, vet, elephant, cruelty.
Trust me, I've left a lot of the best details hidden.
Besides, reading the book is a delight in itself. I can never come close to Sara Gruen's style unless I simply cut and paste the best bits.