A book on songwriting
by Jimmy Webb
This book is an absolute essential for any would-be songwriter. Webb is one of a very small number of songwriters of the rock era who is not only articulate but also musically literate. The only other songwriters of roughly his generation who have both these qualities I can think of are Frank Zappa and Burt Bacharach. With rare exceptions Zappa's work wasn't aimed at the mainstream while Bacharach works with lyricists, so Webb is uniquely qualified to write this.
The book deals with every aspect of songwriting, from music theory to melody writing to rhyme schemes. These are covered so comprehensively that it would be possible for anyone who had never played an instrument or written a song before to pick this up and write a serviceable song.
While not all Webb's advice is suitable for everyone (in particular I disagree with his views on using a rhyming dictionary - I believe this causes one to write unnaturally) this is the clearest, best explanation of the actual process of songwriting I have ever come across. This book is absolutely essential for anyone who wants to become a songwriter.