I'd agree with Clinton's opinion of the Stan Rogers book. It's fairly thin, though, and there's plenty of room for more songs. You can also use smaller print.
I'd like to have stories about each song - a little about what made you want to write it or anecdotes.
The Rogers book is stand-alone. Even if you've never heard a single StanSong, you could pick up the book and play it. The words are there, the melody, and also the guitar tuning and chords in little pictures, so even if you've never played in DADGAD before, you know where to stick your fingers.
You may think that people who would buy the songbook would do so because they've heard the songs and/or own your CDs. I don't know if that's necessarily true. I think they might sometimes buy your CDs because of the songs in the songbook. (You can include an order form.)
Are you concerned about the expense of printing the notes, or of having them transcribed? I'm sure you could find volunteers who could do the transcribing, and put the tunes in a computerised form so you could check if they sound right.
Should the songbook come out, I'd want to buy it. (As long as it has tunes and an order form for CDs!)