Electronics and physical computing is great fun to learn as you get tangible results from your progress. It’s simple and fun to grab a kit or a bunch of components and follow on with a blog or instructable. However, as you progress to designing your own projects and circuits (or to make following other people’s ideas easier) you’ll need some theory to explain what all the different components do and how to put them together successfully.
Fundamentals of Electrical Engineering and Electronics is an ebook primer available online or downloadable as an HTML help (.chm) file. The formatting is a little weak (inter-page navigation links would be appreciated), but the content is clear and concise (including an excellent analogy for Ohm’s law). The book is split into sections: DC, AC, Semiconductors, Digital, Reference, and Experiments.
I spent some thoroughly engaging hours on recent flights reading this, which I’m going to take to mean “FEEE contains interesting material presented well,” rather than “Jaymis is a big nerd.”