It depends on what part of Qt You want to learn. Qt is quite comprehensive framework and went in more then one direction. If You want to create classic desktop applications Qt4 and Qt5 are not that much different. You can either buy one of the books written for Qt4. You have also this (free) book: An Introduction to Design Patterns in C++ with Qt 4
http://ptgmedia.pearsoncmg.com/image...Ezust_book.pdf
I was trying to read this book but I didn't like it, it was c++/design patterns/Qt book, not just Qt (but it's free)
There is also mentioned documentation which is really great and in the end You will spend the most time with it so starting with documentation isn't bad idea. I was learning mostly from documentation, forum and google. In fact I think that this is the best idea. first ideas about Gui and signal and slots mechanism, QObject, moc, qmake You can learn from documentation. All is there.
There are also Qt learning courses on Youtube. I saw guy who made more then 100 videos on Qt. You can find it, interesting stuff.
If You want to create Qt Quick, mobile application I can't help You, I know only that there is seconds veriosn of Qt Quick which (as I remember) wasn't available in Qt4 (but can be wrong).
Added after 8 minutes:
I've just found this:
http://www.amazon.com/Qt5-Blueprints...qt+programming
and it looks very promising.
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