From where to start the sharepoint 2013 development learning

Hi,

I have been working on sharePoint 2010 from past 3.5 years.

Now I am moving to sharepoint 2013, my company currently does not have a sharepoint project in future they may have.

Now in sharepoint 2013, there are various areas namely  

UI development 

Apps

workflows etc.

I want to know which one should I start to learn first of all.

Another question

I have two books of SharePoint which on is better

Microsoft SharePoint 2013 Developer Reference(Microsoft Press) vs  Professional SharePoint 2013 Development ( Wrox)

 If any one can tell me which one should I read.