Accelerated Reader by renaissance learning does the work for you. It will give you the reading level of the book (and as a first-grade teacher, I can vouch for their system being pretty accurate), and if you click on the title, the second screen will give you the word count and a brief summary.
here's the link:
http://www.renlearn.com/store/quiz_home.asp#quicksearch
I looked up R. L. Stine, and it looks like most of the Goosebumps books are in the 20,000 word range. The Bunnicula series is a little shorter, about 14-16K. In general, if it gets over 25K, it's no longer called a chapter book. It would be Middle Grade Fiction.