I run with a crowd of i-bankers, and I bought this book to try to better understand what they do all day. However, this book is a LOT of history, and the entire first Part of the book is VERY basic information relating to what "money" is.
If you learn well through anecdotes, you will find this book both informative and easy to read. If, on the other hand, you are considering this book thinking it will be information about the modern banking industry given in a straightforward way, you're out of luck. In order to understand the industry (or what pieces of it this book explores, anyway) you have to extrapolate larger themes from nearly 500 pages of amost exclusively history and anecdotal examples. In addition, Martin has a habit of describing people in the industry, e.g., "Mr. X, a swarthy fellow I knew while still a fencer at Penn and something of a womanizer besides..." For some, I'm sure this keeps the book from being too dry. I, on the other hand, found these descriptions annoying and diversionary.
In sum, if you're looking for information about the modern banking industry, just read chapters nine and ten, which are well-written, relatively complete, and exceptionally easy to understand. If, instead, you are looking for the story of how banking has evolved, or you just like to read businessmen's tales, then this is the book for you.