Many thanks. I see that 'The Art of Electronics' has a student manual, which is available on Scribd. I'm going to check it out, along with 'Practical Electronics for Inventors'.
I have both 'Getting Started with Arduino' and 'Making Things Talk', the former book being more "this is what we are going to do and this is exactly how we are going to do it" with not much explanation on what's going on with the hardware. So while it was helpful in getting my feet a bit wet initially, it didn't really teach me anything new.
I appreciate the suggestions, feel free to add more.