I saw this question and had to weigh in because I ended up buying the audiobook after a real runaround looking for a free version. Legally, you can't find a full, free download of 'Crystal Core'—it's copyrighted and the author/narrator deserve to be paid for their work. What you might stumble across on some forum links are either pirated copies or scam sites littered with malware.
My own experience? I used a free trial on Audible. Got 'Crystal Core' for free that way, and if you cancel before the trial ends, you keep the book. Your local library might also have it via apps like Libby or Hoopla; that's how a friend listened to it without spending a dime. Honestly, the search for a shady download is more hassle and risk than it's worth compared to those legit options.
It’s a fantastic listen, by the way. The narrator's voice for the protagonist is spot-on, adding this layer of weary determination that text alone doesn't quite capture.