The For Dummies range of books may have diversified into a huge range of areas with mixed success but what they are still supreme at is Software guides. The whole format and idea was developed for this use and it shows. They are concise, helpful, easy to reference and explain things in simple language assuming no prior knowledge but in depth enough so that even the long time user can pick up nuggets of helpful information. Photoshop CS6 is a huge bit of software that cries out for this sort of approach to de-mystify it and make it more user friendly and Peter Bauer's book does just that.
The Dummies book is best for those completely new to Adobe Photoshop and indeed to image processing software. Unlike the other two, it is more general and so includes more on the creative art or design elements of the software. It's well organized, logical and clear. While none of the three books come with a CD of photos, the Dummies is the only one not to provide web-based images that you can work on along with the book. In fact, it's less of an instruction book and more of a general resource, although it is laid out such that you can work through it if you want to with your own images. The trademark List of 10s contained in Dummies works well here - and is less of a stretch than it can sometimes be in the series. For the new user it's very, very good indeed.
Kelby though is still my "go-to guy" for Photoshop. With Kelby you get the feeling that you are being given advice from someone who uses this software day in day out and really knows the best ways to organize your workflow. It's the shortest of the three books and is strongest for those who have upgraded from earlier versions or indeed come up from Elements. First time users will get something out of this book but it's far from comprehensive. Neither is it helpful for the graphic design elements. The biggest loss is that while he provides one of his excellent workflow examples, unlike some of his earlier Elements guides, this is a general one and doesn't detail for example different workflows for say landscape and portraits. I still refer to an old Elements guide of his for this. If you are upgrading though, this is the one I'd go for, but you may need one of the other two for the missing bits.
The Martin Evening book is a veritable brick of a book. It's longer than the other two put together. Comprehensive isn't the work but it's best for those who like to know why things happen rather than just what to do. He explains the technical bits behind the processes well. If you are the type of person who loves to read instruction manuals - this is the one for you. I find it much drier than the other two. Both Kelby and the Dummies range are known for a quirky sense of humour - Evening possesses none of this. I was around 170 pages into it before it got to something you could do with the images you can download from the website. It's a superb reference book to have but less user friendly as a guide. It's more technical and best suited to those who are already knowledgeable about both Adobe and ideally Photoshop.
Irritatingly, all have something to offer and none are cheap. I love the practicality of Kelby and remain a fan - and in fact one of the negatives about his style, his quirky humour, is more restrained here. Ideally you will want to back this up with either of the other two though - which one depends on your previous experience with the software and, to a lesser extent, the type of person you are. If you crave detail and technical information, Evening is unsurpassed. If you are newer and want a more basic introduction, you don't need to be a Dummy to benefit from the Dummies series.