Love this series. This is an adventure game of puzzles, with no hint system. I especially enjoyed the riddles you had to solve to progress on different levels.
This game is probably not for the casual gamer as many of the puzzles will have you scratching your head wondering what the heck to do. But there are walkthroughs available which you may want to have handy. (I hate to have to use hints or walkthroughs but I did with this game) I suggest you leave no-stone-unturned when exploring an area because some of the items you may need are small or blended into the scene.
The story is good but the "cut scenes" are done with a comic book-type of structure. Unimpressive.
I really enjoyed going through the worm-hole teleporter.