The title pays homage to Rudyard Kipling's Just So Stories,[1][a] but the "tales" are strictly scientific, explaining how a wide range of animal features evolved, in molecular detail.

In these chapters, Held explains the mechanics of evolutionary developmental biology, complete with accounts of what genes such as hox, hedgehog, and engrailed do to shape bodies.

[10] The third part is a single chapter providing "An evo-devo bestiary," a long list of stories, such as "How the turtle got its shell", "How the vampire bat reinvented running", "How the quetzal got its crest", and "How the firefly got its flashlight".

The taxonomist Marc Srour writes that Held must be commended for not oversimplifying evo-devo, since, "The need to combine precise genetic and developmental labwork with phylogenetic systematics and homology inference means that simplifying the whole ordeal for a lay audience is extremely tricky."

Srour sets the book alongside those of Stephen Jay Gould and Sean B. Carroll's Endless Forms Most Beautiful as a showcase of evo-devo.

"[11] The evolutionary biologist Larry Flammer "warns" readers that when they look at the pictures or study Held's diagrams, they, "will be captivated by the full-page captions, and probably drawn into the effort to really understand what is happening.

[14] The molecular biologist Arnaud Martin observes that, "As children, we have all wondered about 'the How and the Why' of animal features, and if you are reading this it is in fact quite possible that a similar inquisitiveness still burns within you.

Martin finds evo-devo fascinating, "inherently colorful and well placed to fulfill the dual goal of etiological myths: explaining origins and causes while also stirring imagination and awe.

Overall, the latest opus by Lewis Held Jr. fits that niche nicely, and shines by its ability to span essential concepts and empirical work with enough rhetoric[al] punch.