This was always going to be a hard novel to adapt - the very qualities that make it a great read make a confusing film. The book has a mysterious, dream-like, languid quality - Woolf can slip over hundreds of years in a sentence and the reader admires her prose skill and absolute razor conciseness.
On the screen though a jump of that kind, with no explanation, is just confusing. We detect from early on in the book that it's more of a psychological fable set against a literary / historical background than a naturalistic, historical story with a real plot. But on film all the realistic period detail etc taken in by your eye makes you instinctively expect realistic events. Might have been a better film if done like a Greenaway, so clear to the viewer it's not a 'realistic' story etc. Or if completely re-interpreted, or turned into a feminist polemic - by just translating as closely as possible events from the book to screen it's just thin and pointless. Plus many long, silent, madness-inducing pauses in the film, which obviously you don't get in a book.
There's simply no 'story' in the film, no reason to care, and the only character seen long enough to register is Tilda Swinton's Orlando, who as a distant, expressionless, apparent immortal you just can't care about. We don't even get to know 'what it's like' to be Orlando, and there's no interest in the whys and wherefores of his/her immortality - so no 'threat', no 'learning', no story arc of any kind. All in all I can't recommend the book highly enough (plus it's really thin!) but don't bother with the film.