Now, I'm a big fan of these hidden object adventure games, and I can safely say that there are some amazing ones out there. Sadly, "Crystals of Time" is not one of them.
First of all, the game pretty much leaves you to your own devices for the most part. It's hard to tell which rooms you're supposed to go to next; I kept having to press the hint button to figure out where I was supposed to go. Not only that, you can't easy-jump from room to room using the map; it only leads to certain general areas of the house, the garden, etc. As a result, there's a lot of backtracking involved, and it quickly gets annoying.
Second, the so-called story in this game really has no bearing when you actually start playing. First of all, why does a thief need to break into an abandoned mansion? And those "crystals of time" that are supposed to be super-important? Yeah, you spend most of the game looking for the crystals, but actual time traveling literally only happens in three rooms of the game. Nowhere else! This results in the ending being one of the most anticlimactic I have ever seen. We're introduced to all these characters and pieces of a story, but they don't seem to completely fit together.
As for the puzzles themselves, they're fine. I was pretty much able to figure them all out without any difficulty. But if you like a good story to go with your hidden-object adventure games, I do not recommend this one. At least, not unless you like sitting for thirty seconds waiting for the hint button to recharge.