This is an art book. Due to the theme, there is a bias to Medieval and Renaissance images, but other periods are represented as well, as are angel-equivalents from other traditions.
The text is minimal, a sprinkling of one-line quotes and one page explanations. Unless you'd been wondering about thorny theological issues such as "Does a cherubim outrank a seraphim?" or are so unfamiliar with other religions that you didn't know Islam had angels (for instance) feel free skip over it and just look at the pretty pictures. However, I must admit that I did learn a couple tidbits that I hadn't known previously. I had never heard of Mame Diarra Bousso, mother of the founder of Muridism and a religious figure in her own right. And there is a good paragraph summation of Ethiopian Christian history, of which I suspect many younger Americans are unaware.
The reproduction quality is good and the format of the book overall is pleasing, although a little unwieldy to read, due to it's size and flip-out cover.