Audio Power Amplifier Design Handbook by Douglas Self
is the "must have" book for the audio designer. 
If you need a "beginners_but_not_so_at_the_beginning" book, try with this bible:
The Art of Electronics by Paul Horowitz, Winfield Hill 
Another useful book is the:
Reference Data for Engineers Radio, Electronics, Computer and Communications

You can't forget the:
The ARRL Handbook for Radio Communications

Another "must have" (but this is not a beginner's one):
Analysis and Design of Analog Integrated Circuits (4th Edition)

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