[mhh__]

Can't go wrong with the art of electronics. Not quite a classical textbook but also not a cookbook - takes you from basic theory to analogue to digital to computers etc.

There's not much to it at a basic level - theory wise, you need Ohm's law, Kirchhoff's Voltage/Current Laws, a few theorems (Then you add knowledge of active components, obviously)

N.B. Understanding complex numbers is a big help.