This elegantly written book, published in the very useful Penguin Lives, is probably the clearest, most serious introductory text to any Eastern religion in English. In the first place, Ms. Armstrong, offers us a traditional biographical narrative of Siddhatta Gotama. This biography draws on both very traditional and recent sources and balances very well indeed the demands of writing a lively narrative without losing intellectual rigor. In order to main this rigor, Ms Armstrong draws on the Pali Canon and many English language and German sources. Beautifully integrated into this biographical narrative is Ms Armstrong's thoughtful account of the main concepts of the Buddhist tradition: Anatta, Atman, Dhamma, Dukkha, Iddhi, Nibbana etc. Finally, for the ordinary reader, Ms Armstrong includes a helpful preface on Buddhist sources and a Glossary containing succinct explanations of key Buddhist term. There is also a convenient map of the Gangetic plain at the time of the Buddha. The only criticism to be made of this book is that the author tends to overplay the important of an "Axial Age." This philosophical tic, also present in Ms Armstrong's other books, diminishes the singularity of Buddhist thought and is something of an oddity in this otherwise excellent work.
Karen Armstrong's short biography (though longer than most of the other books in the "Penguin Lives" series) is simply the story of the Buddha's life. She does not mean to explain the teachings of Buddhism per se, though by reading about the Buddha's experiences, you can't help but implicitly learn his basic philosophy. As such, I felt that Armstrong's book adequately introduces the reader to the life of Siddhatta Gotama. She explains most unfamiliar concepts with care, and often makes comparisons to other religions with which the intended readers are probably more familiar. She discusses the limitations of the sources she used to piece together Gotama's life, and tries to keep the essence of the story true, even at the expense of historical accuracy or scientific possibility. And for these things, she will invite criticism. But her attempt was noble and even successful, and if you're curious about the Buddha, I recommend her book.