I think writing a book blurb is like writing the first sentence of your book. It has to hook your reader.
I think the best blurbs are ones that leave me with unanswered questions. Questions that the book will answer for me. What are the Jewels of Anneria? Why does everyone distrust Heather and Picket Longtreader? Where to the cupboards in Henry’s wall lead?
Suspenseful (but still insightful) blurbs are the best ones.
Not all who wander are lost.