Hi Reghu,
My book is aimed towards JavaScript beginners which have some solid knowledge of another C-like language (
Java, for example).
The reason I recommend Dojo is that it is a one-stop-shop, with functionality like;
Cross-browser 2D graphics and charting
Hierarchical extendable widget system
Generic offline storage
Message bus
Data abstraction between widgets and data sources
Unit testing
Customized builds
Internationalization (i18n) for all widgets, including BiDi support
WAI/ARIA support for screen-readers
et.c.
Cheers,
PS
http://unclescript.blogspot.com/