What should I learn this Summer?

I'm in between my A-Levels now, entering my second year in September. One of my subjects is ICT.
During the summer, I was planning on learning Objective C and making iPhone apps etc, and I have a book for this as I'm a beginner, this would be a hobby. I'm a registered and paid developer too for iOS, so it would be good to put my money to work in that respect.

But I also have a huge Access 2003 book which helped during the past year, and having checked with my teacher next year we'll be learning about Access database design and FrontPage. Should I put my time into going through this book and really learning Access instead?

I'm literally neutral about both but don't know which to choose. I can't see myself doing both and doing them well. I'm also trying to learn how to drive too over Summer.

Only you know your own personality.

Neither choice has to be done "well" -- meaning there isn't an end to either of them.

In school, you take several subjects at once. Do you say, "I'll get an A in maths so I won't try to get more than a C in biology."

But, this summer, you don't have to do both simultaneously. Focus on one until you reach a certain point (assuming you reach a good breaking point), and then switch to the other. Go back and forth.

In this way, you'll be ahead on both.