I haven't read any of them, but a co-worker has the first and third books that you have images for. I believe the first is very intensive on mathematics.
I've read the first one (with the blue cover). It is essentially a textbook on how to program written for non-CS type people (particularly in the arts as Processing was always targeted toward a fusion of art and computers as you said). There is nothing wrong with that and I enjoyed the book, but it isn't really a hard-core reference/tutorial.
The Visualizing Data book is great for many different reasons, but it only uses Processing as a tool for some of the examples and doesn't go into much detail on the language itself (IIRC).
I haven't read the other two books, but I think you're going to find that with a project like Processing, which is still in beta (or is it still alpha), it isn't going to sit still long enough for in-depth books to be written about the nuts and bolts of it.
I own the second one with the circles on. It's a good book with a focus being on making code work, rather than trailing off with pages of theory. It's really thick and full of code samples split into handy categories.
I second pdavis, you can never go wrong with an O'Reilly! They have helped my with many languages and you know what to expect.
I own both the first and third of those books ("Processing: A Programming Handbook for Visual Designers and Artists" and "Visualizing Data").
Both are incredibly good books - each with a different focus.
The first is a better general "learn processing" book in my opinion, because it starts at the basics and goes all over the place within processing to share what it can do. It's not focused specifically on "visualizing data" and is a very accessible read. I'm sure some of that is because it reads like it's aiming for an artist and geek audience at the same time.
The second (Visualizing Data) is a book focused much more on human process and methods of telling a story with data by visualizing it, and it happens to focus on using Processing as it's engine. Ben's excellent book (I highly recommend it!) could have easily been written using Flash, Objective-C, JavaFX, Python, or anything else. He gives a good overview of Processing - don't get me wrong there - but the book is really focused on showing how to effectively visualize data.
If you're looking at just "learning processing" without any ulterior motive, I'd recommend the first. It's much more dynamic in it's range of what processing offers and what you can do with it. Very inspirational in fact. If you've got A.D.D., watch out - it's one of those books that will generate lots of ideas in your head. :)
If you're looking for "I want to visualize this stuff up!", then Ben Fry's "Visualizing Data" book is the place to go. You can always expand to the other books or read online when you want learn some of the other interesting nooks and crannies of Processing.
(I also own "Making things talk" - which is a whole different view on the world of Processing - but that more focused on the communications with devices end of things. It's not an intro to Processing, but a "how to use processing with other devices to do some wicked cool stuff" book)
I own the first and the second book. Both books have nice examples of processing code with focus on visual effect. This is something you'll rarely see in other programming books; how you create nice looking output with simple code.
The first book is more beautiful written, has a clearer structure and focuses heavily on introducing processing to non programmers. It gives you a good overview about the languages capabilities, using a nice visual indexing system of all example code. Definitely a good book to read. Don't expect a thorough language description through (you'll have to use the reference documentation of processing for it).
The second one is more the type of a traditional programming book. Explaining everything - from IDE to language grammar etc. You'll find nice examples here too, creating stunning effects from small code fragments. Some concepts are described in more detail here. But if you are a more or less experienced programmer, you'll find yourself skipping many chapters.
I, for myself would buy the first book, because it is more processing like (like the python guys would say - that something is more pythonic ;). You see, coding in processing should be art and the accompanying book should be art too.
Hope that will help.
Btw.: I'd like to read a short review of the forth book and I'm most curious about the following (japanese) one:
Built with Processing (Published 28 March 2007, BNN. 232 pages. Softcover.)
I got "Processing: A Programming Handbook for Visual Designers and Artists", as being an engineer and not a designer, I could skip most of the basic stuff at the beginning, However the book is well written, has good examples and the layout and illustrations are beautiful.. so I can recommend this book..
I am using Learning Processing, the 4th book pictured above, to teach beginning programming to High School Freshmen. It is designed for beginning programmers, so it's not good for your needs, but it has been great for my class. I have read part of the first book, Processing: A Programming Handbook for Visual Designers and Artists, and it is more advanced, giving a fuller treatment of the Processing system.
I've read parts of "Visualizing data" and "Learning processing".
I agree with the others' review on the former one. In particular, you will learn nothing about sound or 3D processing from it. It has a very strong focus on revealing structure in data in a 2D visual way. Consequently, all discussed sketches require external input data. (Many sketches out there don't and are meant to be a stand-alone work of art.)
The latter one is a beautiful book. It looks beautiful, feels good and is well written; excellent craftsmanship! It is the perfect present for your 14 year old cousin to lure her into programming or your art savvy pal to make him understand your fascination about computers. But I wouldn't recommend it to anyone posting on stackoverflow. The information per page rate is just too low. You would be getting bored quickly.
Besides, processing is such an accesible language, that I wouldn't waste to much time on books. Focus on how to build fascinating programs with it. (As any good tool, it is easy to learn, but takes a lifetime to master.)