For the unaware, Whispers Revelation came as a sequel to a mini game called Whispers Room 6 released 2 years ago (found it on google after reading game description somewhere on BF). Have just played Room 6 and I'd vouch it's great for a free game. Not playing Room 6 will not let you miss anything since that there's only little relation between the two. Now you're playing the grown up Lunna, while in the former game, you play as her Dad.
This is definitely a huge upgrade from the free game despite its weaknesses. One major weakness being its great difficulty as other people have already mentioned. If you can bear with it, you'll love this game.
Going back and forth without clear clues are basically what you will do in adventure games. And clearly this is more to Adventure than HOG. Having already played Room 6, I can see that the developer wants to bring in another Point & Click experience. They intentionally did not give many clues in this title but end up making a quite frustrating game. Nevertheless, I was up for the challenge and already went through halfway.
Either you love or hate this game. It can't be both. I choose to see the bright side of this game and love every effort that the developer did right.