It takes you through a brief tour of the DOM, triggers, Manipulation of the DOM, Using Ajax for passing data. There is also a entire chapter on writing JQuery plugins, which does seem a little out of place. However a saving grace is the Appendices that deal with a number of newbie type mistakes that can and do occur with the use of a library of this nature.
Web Standards and the use of unobtrusive development techniques have not been forgotten with this book. It even takes a leaf from Jeremy Keith with some Hijak like methods. This is all good, and I can recall smiling away when I was reading this book over these very points.
The book is also a little dry in tone, not to the extent that it is unreadable. But I did find that it was best studied from in limited periods. Layout wise the book is reasonable, a minor point: more white space around the code examples would have helped the clarity of the examples.
Learning JQuery is reasonable book for a designer to learn JQuery from. If you know your usability and accessibility (and you should) then you will find some minor errors, but you can easily get around these.