If you want to read a book about biodiversity, read David Quammen's "Song of the Dodo." That is an excellent book that is more entertaining, more informative, more scientific, better wwritten, core comprehensive. It is everything you wanted to know about biodiversity written in terms a layman can understand.
This book, on the other hand, is a quick gloss over of a very interesting topic. It jumps around a lot. It does not cover anything in depth. It does not explain how biodiversity is studied. It is not particularly well written, although not terrible. And it does not get its facts right. I am sure the author is not a biologist and has only a superficial knowledge of this topic. Here are some examples.
He refers to rainforest as "jumgles," using the terms as interchangeable. This is not true in a scientific sense. Rainforests are original, diverse forests with a clear understory. If you've ever walked in a rainforest, you are amazed at how little growth there is on the ground. There are a ton of roots to negotiate through, but very little actual growth. Jungles on the other hand are disturbed, second growth forests that are rife with undergrowth, young trees and lacking in biodiversity.
At one point he states that Komodo dragons are the largest of all living reptiles. This is eimply not true. Komodo dragons are the largest living LIZARDS. There are several crocodilians that are much, much larger, and even some sea turtles weigh more. The largest Komodo dragons are about 10' long and weigh around 150 lbs. The largest crocodile gets to about 23' and weighs around 2,000 lbs. That's quite amistake to make. Anyone familiar with reptiles at all would not make this error.
The author also refers to Galapagos marine iguanas as "These most seaworthy of all reptiles." Actually, again, they are the most seaworthy of all LIZARDS. Marine iguanas spend most of their time on land, only going into the water to feed. Sea turtles spend nearly their entire life in the sea. Females come out to lay their eggs but in many species males never emerge once they enter the sea as hatchlings. Sea snakes are even more marine in that they even give birth in the water.
A wuote: For many species, islands greatly reduce two of the key pruning agents of evolution--predators and severe competition for food--so island relatives help depict what mainland birds would become like if these same cushy conditions existed on continents. I agree that islands generally reduce the number of species of predators, but there is still intensive competition for food. The difference is that this competition may take place withing a single species or group of species. For example, Darwin's finches are an example of resource partitioning due to competition for food. Island environments are not "cushy." They are sometimes brutal due to the limited resources available.
Anyway, you get the point. Due to the fact that the author is not really familiar with biology, he makes several fundamental mistakes. These should easily have been caught by an editor with a biological background and, in any case, can be checked by simply looking them up, at least some of them, on Wikipedia.
Nevertheless, it is a book on an interesting topic and the majority of it is more or less correct. Still, if ou are interested in this topic at all, I strongly suggest you read David Quammen's book.