Hidden in Time: Mirror Mirror is like a Where's Wally? book, mixed with a mysterious story.
The basic mechanic of Hidden in Time: Mirror Mirror are like all games of this genre - you can play timed or 'relaxed', and your job on every level is to find objects, from a list, that are hidden in a scene amongst all sorts of other junk.
Between each level the story unfolds in book form, and is accompanied by eerie music. There are mini games as well as the main hidden object parts, which are puzzles based on using mirrors to direct light beams to reveal clues, or spot the difference mirrored images. These make a nice break from the main game.
If you like this type of game, Hidden in Time: Mirror Mirror is great - atmospheric with well hidden objects. It has some quirks too: There are some really strange objects hidden in the games, and you may well find yourself reading the name of an object and having no idea what you're looking for! There are a limited number of hints, that show you where objects are, so you should never get completely stuck.
Challenging and varied enough to keep you interested, and with an intriguing story to boot, Hidden in Time: Mirror Mirror is a solid hidden object puzzle game.