R.L. Stine -- I'm a HUGE 'Twilight' Fan ... Or Am I?

R.L. Stine -- the mad genius behind the "Goosebumps" books -- says he LOVED the first "Twilight" book ... but not enough to pick up the second one. Sooooo ... literary diss??

Here's the backstory ... Stine was out in NYC yesterday when the topic inevitably turned to Stephenie Meyer's vampire books.

Stine says he liked her original book, but admits he never moved on to "New Moon."

You'd think ... if a fellow best-selling author REALLY "liked" the first book of a massive series, he'd move on to the next book. Then again ... maybe he's just really busy.