For starters, the game has issues running on modern systems- do a search for the Revamped mod, which is small and easy to install. I didn't encounter any bugs after adding that.
As for the game itself, it shares some of the weaknesses of Soul Reaver 2- it's extremely linear, with none of the exploration or secrets of the first two LoK games, just a long series of tedious battles and easy puzzles standing between you and the next cutscene. The combat is very repetitive and gets old quickly, and while it's not too difficult, on rare occasions the enemy will decide to cheese their unblockable super damage move five times in a row, usually with no time to dodge, forcing you to replay long sections every now and then. The special skills are clunky and awkward to switch between and use, which the game requires you to do often.
The game lacks the intrigue or sophisticated dialog of other entries in the series, being mostly simplistic bickering between Kain at his most shallowly evil and various vampires, several of them dressed in ridiculous bondage gear- though it is all, at least, well voice-acted. You can skip this entry in the series entirely and not really miss anything terribly important to the overall storyline that isn't summarized in another, better game.
The graphics are muddy and ugly, with lots of brown brick industrial areas and murky water, though it gets slightly better after the first few levels. The concept art in the end credits indicates that they had some pretty interesting ideas, but the majority of them didn't make it into the game and the ones that did were ill-served by the limitations of the Playstation 2 era. The cutscenes are unskippable, even the ones in the midst of boss battles or in long stretches with no checkpoints.
I'm not sure what else to say- it's just not a very good game. The level design and gameplay were good enough to get me through to the end without wanting to simply drop the game and forget about it, but only barely. It might be worth playing for Legacy of Kain completionists who love the series and don't want to skip anything (which is why I finally got around to doing it), but you're going to be disappointed and you're unlikely to ever play it a second time in the future.