Blurbs, or short descriptive material to promote a book, may be impossible to legally share do to individual copyrights of the authors or publishers.
The Goodreads API has many endpoints, and they include this note:
Book cover images, descriptions, and other data from third party sources might be excluded, because we do not have a license to distribute these data via our API.
In contrast, the book metadata can be shared (ISBN, author, publisher, etc). See, for example, the Book-Crossing Dataset.
So, in order to get a big data set of blurbs, you'd have to contact (large) publishers and ask for access. I noticed you have university affiliation, so you should mention that it is for non-commercial purposes.