I think the blurb and the other customer review nicely encapsulate what this game is about: “deadlier skills, a darker heart and a craving for battle”; “intricate new combat system”; “unique fighting style”; “projectile attack system”; “brutal, unrelenting monsters”; “devastating new combative powers”; “variations in fighting gameplay”; “more variety of moves, weapons and enemies”. I think that sums this game up nicely: the only thing missing is the BFG9000.
Some other characteristics: (1) Combat is harder than in the first game, “Sands of Time”. Puzzles are similar, though there's a lot more running from A to B. (2) It puts in some effort to emulate the stylised gracefulness of its predecessor; while it's not completely successful, the character movements are certainly more varied. They're just not as stylish.
Things that this game does not have: the strong sense of Persian-ness, or at least foreignness, that its predecessor had (instead it feels like generic swords-and-sorcery); a captivating story; a compelling soundtrack; depth of characterisation; charisma; a sense of humour.
“Warrior Within” is designed for people who wanted “Sands of Time” to be a combat game. I think it's worth pointing out, however, that combat is not the reason people fell in love with “Sands of Time”.