First, let's get one thing out of the way: this is not an Indiana Jones clone. Indiana Jones was himself based on and a tribute to Allan Quatermain (H.R. Haggard, 1885) and Professor George Edward Challenger (A.C. Doyle, 1912). And the protagonist of this game, James Lee Quatermain, Allan Quatermain's great-grandson, has a completely different personality (and a couple of jokes in the game point out those differences).
But the feel, the mood and the ambiance are the same, so Indiana Jones fans WILL enjoy it.
When Lucas created Indiana Jones, he was trying to recreate the feel of 1930s action serials. This game succeeds in re-recapturing that feel and it's the main point in favor of this game. The scenery is beautiful and even the ceilings are worth admiring (not to mention that they also sometimes hold clues or things with which you can interact). The plot is unoriginal, but still engaging. The puzzles are logical and well integrated in the flow of the game. There's an interesting selection of weapons and they feel well balanced. You can kill an unarmored human enemy with one or two bullets, but they can return the favor, so you can't play this game as if you were Rambo. The journal, a very obvious copy of Henry Jones' journal, is not interesting to read, but it is very useful. Sometimes it just provides a hint for a puzzle. Other times, it's a key part of the puzzle and you can't solve it without consulting the journal. A nice touch is that the foreigners you meet speak in their native tongue, which makes it feel more authentic.
The game is so linear that you might not notice a difference if they put it on rails. Backtracking is impossible because your entrance is invariably blocked every time you enter a new zone. I can't see this game having a lot of replayability. It uses the lazy, antiquated, and much hated checkpoint mechanism. Sometimes, the chekpoint is so far back that it can take 10 minutes to replay the part leading up to your death. Movement and shooting are ok, but in almost every other part of the interface, it feels so much like a console port that it's practically a slap in the face to PC users. You can only scroll back and forth between your weapons; you can't select the one you want directly. The POV is very strange and gives you the impression that you're only 4 feet tall. This feeling is exacerbated by the fact that you're unable to jump on a crate that your grandmother could jump over. The jumping is so sluggish, in fact, that it's more irritating than useful. There are glitches that will let you get trapped between two objects and your only option is to restart from your last checkpoint.
The acting is a bit on the campy side, but not so much that it ruins the game.
But for all the little irritants, this is a fun little trip into an Indy-esque world and I still recommend it, though not at the ridiculously high full price.
One odd thing: the optional Allan Quatermain revolver that comes with the Deluxe edition is worse than the default Webley; it's just prettier.
Two suggestions: (1) don't swap your basic revolver for a better one you find. The basic revolver has infinite ammo, your new one does not! (2) If you're so inclined, you can change one of the ini files to give yourself infinite ammo for all weapons (instructions are on the web). A nice side-effect is that you end up keeping almost every weapon you find (you can usually carry only two), but you occasionally get stuck on one of them until some random event in the game clears the buggy state and you can switch weapons again. It's a fun way to run the game a second time.