One of my favorite covers as far as the kid depicting Rachel looking basically exactly as I envisioned her from the descriptions, though that's probably a lot to do with it being an early book in the series and sort of influencing that. I always found that especially with the later books some of the covers seem a little off with the actors/models, especially in the big montage one towards the end with all the kids arranged on the inside cover. I think they switched people a few times throughout the series too. But books like 2, and the first Marco one (5?) really matched the visual in my head like 100%.