So a new Humble Bundle has appeared that’s aimed at mobile devs which is cool!  It contains a large range of books by Packt which will help any Mobile Dev improve their skills, details below:

https://www.humblebundle.com/books/mobile-app-development-books

I am sure I have done it before, but I would also like to point out that Packt also gives away a free book every day!!!  Claiming it is one of my daily tasks!

https://www.packtpub.com/packt/offers/free-learning