As you read through, some of the characters will have a very small storyline surrounding them (the talking tree is the best example of this) with each following instalment for them making their life just that little bit more sad. It's a strange sense of humour really, it shouldn't be funny at all, yet it is. I suppose it's because what happens to the characters is so ridiculously sad, that it would never happen in real life, and so we're laughing more at the absurdity of it, rather than anything else. I suppose the contrast of bright colourful characters being so utterly depressing is another factor of the book's enjoyment.
What I quite like about this book is that it, unlike nearly all other books, really benefits from being read in a group rather than being read alone. It's quite fun to look through the book with a friend, and if you find one which is particularly funny you can remember the page and show it to somebody the next time you see them. It's quite a small book, so it'd be quite easy to carry it around with you so that you can show it to people.
While good, this book is far from perfect. A big setback is the price, it costs just as much as an average book (and it is as nicely made and everything, as the average book) but since it is just collection of funny pictures along with sad captions, the price does seem a little high. Plus, I did find that they weren't all hilariously funny; while some of them definitely very funny,
(for example, a dodo replying to the dinosaur with "All MY friends are dead.") others were a little hit and miss (for example, a cassette tape saying "all my friends are obsolete"). Overall, I'd give the book a 7/10