I have bought several books on using speedlites over the last couple of years. Each time I get one I think this is going to be the one that explains it all to me. Unfortunately, I've generally been left just as confused as when I started.
But this one is different .... Syl Arena's book is a MASTERPIECE! It starts right at the beginning and assumes no knowledge, some of the things in the early chapters I knew, but not everything, so I felt like I was learning straight off. Then as I read on I kept thinking I'd be getting to the complicated bit soon, but the truth is that Syl translates the complicated bit into plain English. It's like waking up and finding you can suddenly speak Spanish! Not only is it clear and simple, but it's a real page turner too, hard to put down.
The book covers everything you could possibly need to know, right down to the types of battery you could use and the pros and cons of each one.
I can't recommend this book highly enough. If you are only going to buy one photography book this year .... make it this one!