Juliet Dove, Queen Of Love by Bruce Coville
Mr Elives' Magic Shop seems to appear from nowhere - and disappears just as fast! Never in the same place twice, it sells only the most exclusive wares...A talking toad, anyone? A dragon's egg? There's plenty to choose from...All Juliet wants is to fade into the background - for no one to notice her. When a strange woman in Mr Elives' shop shows her a beautiful amulet, Juliet knows she must have it. The ancient necklace has a very strange effect on every boy she meets. Worse still, she can't take it off! And its power seems to be increasing...