The Anthropic Principle is actually quite an interesting theory. The reason the Universe exists the way it does is because if it existed any other way then we couldn't be here to ask why the Universe is the way it is. For example, if the gravitational constant was a bit stronger then stars would collapse into black holes before they could ignite. If the electromagnetic force was a little weaker then electrons would stream off from protons and atoms could never form. If the strong force was a little stronger then nuclear reactions would be impossible and stars would never light up.
There are, in fact, many possibilites associated with the Anthropic Principle. The first is that there are an infinite number of universes and we evolved in this one because this one happened to have the right combination of constants. Another, far more daring theory, is that the Universe needs a quantum observer in order to actually exist.
All this is in way of introduction to my review of the book, The Constants of Nature. This could have been a very good book as it discusses a lot of the ideas around the Anthropic Principle and associates it with the constants of nature, including the fine structure constant. Unfortunately, the author doesn't do a convincing job nor does he go deep enough to make the book a very interesting read.
Some of the errors in the book are comical. For example, he states (although I am sure he doesn't mean to) that solar eclipses are caused by the Earth's shadow falling on the Sun. But others are more subtle. For example, he discards the quantum observer theory by claiming that any observer, even a photographic plate, would serve the role of an observer. However, a quantum physicist might tell you that until someone actually develops and views the plate that what is on the plate is still only a quantum probability.
The book isn't all bad and parts are actually quite fascinating especially if the topic is unfamiliar but overall there must be better books out there that cover similar topics.
You can see the full review here.