In addition to these two titles:
this series includes Birds, Fish, Invertebrates, and Mammals. Let me just start by saying that these cover photos immediately made me WANT each of these animals (well, maybe not the pterodactyls), which is probably one reason many of them are endangered. When even tween pop idols (ahem) are caught smuggling illegal pets, it's hard for a species to get a break. Disappearing habitats, pollution, fashion trends, bizarre medical myths - it's all just too much, without adding misguided exotics enthusiasts!
Each of the books in this series begins with a simple explanation of that class of animals, then delves into some specific species. Unfortunately, these seem to lack some of the structure of other series Lerner produces - the text seems to meander a bit, and explanations are not given as to why some of the species are endangered. A young reader might have a hard time looking at the Chinese alligator and understanding why it should feel threatened!
Some of the other usual strengths are still there - glossary, web sites to visit, bright photographs and simple text, etc. Hopefully, these are just a fluke, and not a sign of a good thing becoming too mass-produced.