Well well, you likely guessed this was coming in a near future; This is Oliver Jeffers' Lost and Found, the original children's book the animated movie of the same name is based on. The adaptation was so darn good I simply had to see the roots of the whole thing and it doesn't disappoint. If you liked the film, you'd be glad to know the book as as great – and vice versa. And it has to be said that Jeffers' stylized penguins are absolutely adorable!
Also, when I was doing a quick fact check and link retrieval for this post, I noticed that there is a sequel to this book, called Up and Down, published in 2010. I guess it's back to online book store, then!