The Whispered World falls into the realm of zany adventure games, complete with a morose, unlovable schlub for a protagonist. Unfortunately, zany and surreal adventures invariably involve a certain amount of "try everything on everything" to progress, and this runs afoul of the crappy interface.
Frequently, The Whispered World fails to register a mouse click, so you never know, when trying an object on another, or an object on part of the environment, if it truly
did nothing, or if the game simply didn't notice your attempt. Sometimes it takes four or five clicks to get the game to respond. After the third time that I gave up on a puzzle, checked a walkthrough, and discovered that the correct solution was, in fact, one of the first things I had tried, except that the game hadn't deigned to notice at the time, I gave the whole thing up as a bad exercise in frustration.
If you're masochistic enough to endure this game, make a point of clicking several times when trying anything; hopefully one of the clicks will register. The art, incidentally, is quite beautiful, it's simply a shame what aggravating hoops you must jump through to see it.
(And, yes, my mouse works fine in all other applications, so I feel confident blaming the game engine for this non-responsiveness.)