Just finished rereading it, actually! I have a battered physical copy, but last I checked, 'Little Big' by John Crowley isn't typically free on major platforms due to its cult classic, non-bestseller status. It's often under copyright. My library's digital service, Libby, had it as an audiobook, which is a fantastic way to experience the lush prose—Crowley's narration on the official audiobook is stunning.
For reading online, your safest bet is a purchase through Google Play Books, Apple Books, or Kindle. Sometimes you can find used PDFs floating around from very old scans, but the formatting is usually a mess and it feels wrong for a book that's so much about the physical craft of writing. Honestly, buying the ebook supports the author for a work that deserves it. The dreamy, layered text really needs a clean digital or physical page to get lost in.