If you don’t know anything about the banjo, just like the idea of giving it a go and want to find out more before splashing the cash on one, then this is potentially a 4-star book. For everyone else, it’s a 3-star book.
Though it’s over 350 pages long, only about 100 pages in the middle are actually about playing. The rest covers everything from a bit of musical theory to the history of the instrument to equipment and buying advice. This universality, making sure absolutely everything gets a mention, is not unusual for books in the Dummies series, but here it may be too comprehensive for its own good. If, for example, you already know you want to play bluegrass style rather than clawhammer (or vice versa), that 100-page practical section shrinks even further. You’d be better off getting a book dedicated to your chosen style.
For everyone else, however, it’s not bad value, in that there are plenty of books for beginners that may be more practical, but which are also more expensive and actually have fewer than 100 pages of practical advice anyway. And if you don’t know which style you want to play before you start, this book gives a good taste of them all (though of course the emphasis is on the American sound rather than Irish folk, for example).
The practical section is mostly exercise-based, featuring various rolls incorporating the technique it is currently trying to teach you, rather than actual songs (or bits thereof) where that technique is used. There are still some songs to play, but they are the same old standards you will find in any banjo book (Boil Them Cabbage Down, Cripple Creek, etc).
Dummies books used to include CDs featuring audio tracks to play along with, but these are now all accessed online. There are also good videos on the website that will be very helpful to the complete beginner, especially if they have never played a stringed instrument before.
Perhaps not unsurprisingly the book is very American, but unlike certain other Dummies books there has been no attempt to Anglicise certain advice, even minimally, to make it more relevant. This does make the buying guide pretty redundant outside North America.
So, not a bad place to start, but I imagine most beginners would end up buying another, more specific book, within a month or two.