On the face of it, monster books are probably the easiest d20 books to create. Pull together a list of attributes and powers, slap a description and a picture on it, and you've got yourself a monster. Lather, rinse, repeat, and you have yourself a book.
Of course, it's really nowhere near that simple. While it might be easy enough to generate lists of statistics, it's a lot harder to differentiate those sets of statistics from the ones being put out by everyone else. The real challenge of creating a monster book is offering a collection of creatures that is not only distinctive enough to stand out from the crowd - that essential 'buy me!' hook - but also 'mainstream' enough to be useable by the majority of gaming groups.
The Kid's Coloring Book O' Critters certainly manages to meet the 'distinctive' criteria. I think most members of the ENworld community would be familiar with the story behind this product and that the monsters within it originated in the imaginations of an 11-year old and a 7-year old. Ambient have very sensibly made the most of this in their marketing of the book, and have - as the book's title suggests - even gone so far as to make this d20 product double as an activity book for children.
Of course, this still leaves the question of whether the book is actually a worthwhile investment as a d20 product. So what do you get for your six American dollars?
Well, first of all you get a nicely-laid out, 43 page PDF, with bookmarks for all of the monsters (including their CR beside their names). Here's no index by CR or by creature type, but Ambient have indicated they will be releasing an index-by-CR as a free PDF. The book is laid out in landscape format, which makes for easier viewing on the monitor, particularly in full screen mode. There are a few typos sprinkled throughout the document, but nothing that interferes with the meaning of the text.
Each monster gets a full, single page, including picture (Dragons get 2 pages, due to the extra tables and descriptions required). This is handy for printing, as you can simply run off the single page with the monster you need for tonight's game. The illustrations of the creatures are always placed on the right-hand side of the page, and are situated so that they can be shown to players with nil or minimal text showing. In fact, the book's layout in general is good: Ambient have done a good job.
A quick word on the subject of the illustrations: most have been done by the young authors of the book, though a few are done by industry professionals (artists and non-artists alike). I would have preferred that the illustrations all be done by the girls, or all by professional artists, as the varying styles tend to clash a bit, but this is only a minor quibble.
What might be more problematic for some groups, however, is how to use the girls' illustrations in their campaign. A DM who would readily show their players a picture of a goblin or werewolf might balk at unveiling some of the illustrations from this product. An obvious route around this is to make a child the only witness of the creature, presenting the illustration as their rendition of what they saw, but that can only be used so many times. Fortunately, the text for each creature includes a detailed description, which can be used by those who are reluctant to show the pictures at the gaming table.
But what of the monsters themselves? There are 33 in the book, including two varieties of dragons with full, twelve stage progressions. Almost all the creature types have at least one representative: only oozes and shapechangers are missed. Given the powers of some of the creatures in the book, the latter omission seems odd: the kittyrar, for instance, would have fit the shapechanger type quite readily.
Setting aside the two dragons, the CRs of the creatures tend toward the lower end of the scale: only one monster has a CR over 9. I don't personally consider this a problem, but it will mean that it is less useful for those groups who are heading toward epic levels.
The majority of the creatures in the book share a definite sense of whimsy (one of the few exceptions are the shramp, which have a sinister, Cthulhan aspect that is quite at odds with most of the entries in the book). This can be particularly evident in the names: the Ghoul-goly Moog-oly comes to mind as the premier example. This is by no means a bad thing, however, as it gives the collection a cohesive 'feel'. This is the kind of d20 monster book Roald Dahl would have written: which is quite a compliment, I think! While they might not suit all tastes, the creatures in these pages would work exceptionally well for a campaign with a 'Brothers Grimm' feel, or for any group with a taste for the unusual or humorously macabre.
Fortunately, this sense of whimsy does not mean the book is useless to those who prefer a more 'classical' monster palette. Many of the creatures can be readily used in a typical D&D campaign with no or minimal changes. The Ghoul-goly Moog-oly, for instance, if given a more intimidating name, would serve admirably as a macabre alternative to a Ghast, as its infectious touch strips adventurers of their muscle control, and sets them on a helpless, spasmodic 'dance'.
There are a couple of minor mechanical gaffes in the monster write-ups, either because they don't seem to fit the current edition's rules (the Lumis have an ability which allows them to "reduce the casting time of a spell by 1". One what?) or because they don't seem very logical or intuitive (the magical capability of one race is based on the square root of the number of them present - but with no rules for how close together the individuals need to be, or why they wouldn't simply split up into smaller groups, since they would get proportionately more 'bang for their buck' that way). Ambient's understanding of the jumping rules also appears incorrect.
These are very minor issues, however, and do not detract from the fact that the Kid's Coloring Book O' Critters is a good product, with interesting, distinctive monsters. And of course, if you have children, game with children, or have a taste for things that are a bit on quirky side, it's an excellent product.