I bought this book because of the illustrations. I'll buy the sequel for the story.
Illustrations are a rarity these days, even in YA, and these (by one Keith Thompson) are detailed, charming and definitely go an extra mile in bringing the characters to life. [Though I wish the image used for the girl-in-disguise had been used for the boy, and vice-versa - the pictures just seemed so appropriate for the opposite characters!]
Anyway, the illustrations made me curious enough to read the blurb, the blurb made me interested in reading the book, Book Depository made it cheap and easy to get the book, and it was a one-sitting read once my paws were upon it.
Despites some niggles (How does one remove a coat while strapped into a harness? How does Darwin manage his genetic engineering?) this was a fun, fast-paced story with likeable characters, an intriguing plot, and plenty to make me keen to read on. It looks like it will be at least three or four books to the series, and as ever with series I wish I'd discovered it at the end, rather than halfway between the beginning and the middle, and I'm guessing in a spoilerish way that whatever is in those eggs is likely to "impress" on the first person they see.