For technical aspects of Song and Lyric Writing, these books are essential:
‘Writing Better Lyrics’, 2nd ed., by Pat Pattison.
‘Essential Guide to Lyric Form and Structure’, by Pat Pattison.
‘Essential Guide to Rhyming’, by Pat Pattison.
‘6 Steps to Songwriting Success’, by Jason Blume.
‘Shortcuts to Songwriting for Film and TV’, by Robin Frederick.
If you are looking to expand your palette and gather ideas and inspiration, these books are excellent:
‘Inside Songwriting’, by Jason Blume.
‘101 Songwriting Wrongs and How to Right Them’, by Pete and Pat Luboff.
‘1000 Songwriting Ideas’, by Lisa Aschmann.
To educate and empower yourself on the business and legal side of songwriting, I recommend:
‘The Plain and Simple Guide to Music Publishing’, by Randall D. Wixen.
‘This Business of Music’, by Krasilovsky, Shemel, Gross, and Feinstein.
‘All You Need to Know About the Music Business’, by Donald S. Passman.