Yes this version takes liberties with the book, cutting away much of the historical detail. But it works (or I am a philistine) allowing dramatic licence to hold sway over historical accuracy (the book is overly long anyway, and would have benefitted from some serious editing). I remember watching this as a little girl one winter's afternoon and thinking how impossibly romantic. It really brings to life the story and the sense of wildness that surrounds Exmoor.
This is far superior to the recent BBC version--with its lacklustre protaganists and little chemistry between the leads. Here the romance sparks, we have a headstrong and wilful Lorna, willing to risk her very life to be with John-- far better than Amelia Warner's pitifully bland performance. Similarly Sean Bean is brilliant as the reckless and wild Carver Doone (if I'm honest I bought this just because he is in it-- gorgeous, gorgeous man) much more realistic and manly than the modern version's, Aidan Gillen, who simpers and smirks his way across the screen. (Perhaps its because he was so awesome in "Queer as Folk", but I can't help feeling he "minces" around as Carver Doone--- its really off putting!)
Then you have Clive Owen as John, another gorgeous addition and far more passionate a lead than Richard Coyle. Sorry-- this version may be lower budget, but its far superior in entertainment. Just don't look for literary or historical accuracy.