The last book I read about people dissapearing into magical paintings was Mirrorscape... and that was awful. This, however is a mystical, imaginative take on an old idea. The character's are a little cheesy - Sunni, who has a crush on someone way older than her, her annoying younger brother and the guy that fancies her... you know how it goes.
The layers of the painting, leading to different worlds, was an amazing idea. There's a maze in this, which reminded me strongly of Maze Runner crossed with HP and the GOF.
A fantastic read for all ages (even if you just want to learn how to say Chiaroscuro!).