The number of frameworks and libraries available is just...enormous !
To select which one is the best for your needs is just impossible...really !
Backbone, Angular, ExtJS, Dojo, ... are surely great ones but I'm not fond of the way to code : add attributes in HTML Tag and inline JS.
Enyo is the only one I found what doesn't need this : you only need to code JS and optionaly improve your CSS.
Of course Enyo, in fine, produces the same thing but you, the coder, don't need to code pure HTML and your (web) designer will only produce his CSS.
Coding in Enyo is like coding in full AS3 with CSS.
So, I ended reading this book.
The Up and Running collection of O'Reilly seems to be a "Introduction" collection (like the "Instant" of Packt) : only 80 pages.
I read it on my ebook reader but it should be read on a full PDF Reader (desktop or tablet) because there is a lot of link to follow : code is available at JSFiddle.
You should know all the information available on this book is available on Enyo website.
I'm still trying to understand what backbone is for example
So why read this book ? Because Roy Sutton wrote it in a way which gives you the feelings you became an Enyo ninja in 1 day ! :)
You could save 8$ and just read Enyo's doc but it would take you longer to understand some points (like kinds and a layout).
I was really interested in Enyo before I read this book, I'm now really a fan.
You'll need to read more on Enyo website to really become a ninja (the install/debug/deploy part in the book is just unuseful as-is) but thanks to this book, I'm now ready to fight with the language I hate the most after VBA.