I bought this e-book just the other day. I got sick of trying to piece together various out-of-date tutorials and following the API docs online. Whilst you can't say the API docs aren't all there, I think it's probably too much. The hide inheritance members button at the top is a must!
However, the learning curve for Ext JS is HUGE and an approach such as "Learning Ext JS" is what's called for, even for competent programmers. I found the Apress "Practical Ext JS Projects With Gears" to be far too centred around the example scenarios, whereas, "Learning Ext JS" is perfect for somebody with a use in mind but just wants to know how all the widgets work. The Gears book would be ideal for somebody with no real idea in mind and plenty of time on their hands to "see what this Gears/Ext JS caper is all about" but if you want to just get to the point of how a grid works, or any other widget, then you're going to have to read through a lot of verbiage to answer your question.
I've also got no problem with the licensing. I use Ubuntu and prefer open source software, and if you're FOSS too, then there's no problem with Ext JS. If you're commercial, then the rather meagre licensing fee for Ext JS is hardly going to make you ditch it and piece together all that cross-browser-Ajaxy-goodness yourself! Whilst jQuery is nice and I prefer it's leaner syntax, its plugin repository is getting tad messy these days and jQuery UI only has six widgets. Can't beat Ext JS if you're not a FOSS license zealot and you just want something to take the pain out of RIA development. Life's too short to get hung up on things that don't matter.