I don't actually own the game on GOG, as I bought it on Steam before it got here. However, I have to say I greatly enjoyed playing the game.
However, as some other reviewers mentioned, it is vastly different from the other Lara Croft games. Gameplay-wise, there is less platforming and the puzzle bits are incredibly simple. It is more action oriented, and has you mowing down waves upon waves of baddies. There are also a TON of collectibles, unlike the previous games.
Story-wise, you aren't playing an ass-kicking badass adventurer. You're playing as Lara Croft before she became Lara Croft, an innocent young woman just trying to survive in the harsh reality she's been thrust into.
TL;DR: If you're looking for 20-25 hours of action oriented entertainment, buy it. If you're looking for platforming and puzzles, this won't scratch that itch.