This is the best, most comprehensive treatment of available data (which has grown some) and theories (which have grown but not multiplied) on land vertebrate extinctions of the last 100,000 years. If you are a mammoth/sabertooth extinction hound, this book will feed you better than any other. It does require some specialized knowledge in a few chapters, but the gist is accessible for the educated layperson. It's worth hunting for or buying used.
A more recent offering, though briefer, is "Extinctions in Near Time," Ross MacPhee, ed.
I appreciate the candor in labeling two of the major sections, entitled 'the theoretical marketplace: geologic-climactic models' and 'the theoretical marketplace: cultural models' which encompass variations on each of the two main theories for the extinction.
In addition to theories, the book describes the various mammals as well as their pattern of disappearance region by region worldwide. At 867 pages, it will keep you going for a while, but it's worth every page.
There is only one chapter on birds, only passing references to a tortise, lizard, or fish, and nothing on plants. I would love to find similar treatments for changes in characteristic flora for the same time period.