I have read only two books on songwriting in my life. So, as far as formal education of songwriting, I am lacking. I picked up some things from each of these books, but I don't think either gave me any great skill that I wouldn't have otherwise.
What these books did for me was make me hypersensitive to the songwriting techniques used by those artists I enjoy. As I listen to a song, I analyze how the verses are formulated to go with the chorus. I ask myself why the artist chose certain words, or made things vague. So, the time since reading the books may be more of an education than the time of reading each.
Some books about songwriting are better than others. In this case, Writing Better Lyrics was what I needed most. I am a more natural music writer, but it was difficult for me to make the transition to seriously edit my own lyric writing. What you have to learn to do is cut out the crap, revise, and then cut out even more crap. If there's anything left, then you have a song worth keeping.
One common thing that amateurs like me often do is write lyrics that don't match perfectly with the meter and length of time for each line musically. I am still working on this, and I think mistakes in this way can actually enhance song lyrics. The professionals seem to do this naturally.
Luckily, I have kept both of these books to look over when I need to go back and do some revision. Unfortunately, neither of these books will create inspiration or motivation to write, so they are more like objective feedback than anything else. I have always been the type to jump in without reading, and that's the best way to start a song. Sometimes a song can stand alone unedited, unrefined, and uneducated.
Music for me is about feeling, not logic and education. The feeling in music should always come first, because if it's not there you have nothing worth hearing. However, logic and education can make writing more efficient and effective. I still have a way to go with both feeling and education, but I have a humble start.