It's difficult to give an exact number because it depends on how you define "book":
* Standalone novels: He has written over 20 standalone novels.
* Series: He has several multi-book series, adding more books to the count.
* Co-written books: He has co-authored books with other authors, which can add to the total.
* Short stories and anthologies: He's contributed to numerous anthologies and written short stories, which may or may not be included.
To get a more accurate count, you can visit Neal Shusterman's official website or his page on Goodreads. These resources usually have comprehensive lists of his works.