Hi Barry,
I just picked up Beginner Fingerstyle Blues by Berle and Gallo based on a recommendation on another thread.
https://www.amazon.com/Beginning-Fin.../dp/0825625564
I like the book. It really does start pretty much at the beginning, assuming you know basic first position chords. The first 75 per cent of the book is all exercises and 12 bar blues in familiar keys, and some of them are pretty musical. I was able to play most of them (not at the author's tempo, LOL) pretty quickly but I found them very worthwhile. There are 5 tunes at the end of the book I have yet to dig into, but they look interesting. Comes with a CD, too.
Another book that I use a lot is one I have never heard mentioned here, I only have it because about half of what my teacher assigns to me is from it. Tommy Flint's Fingerstyle Anthology.
https://www.amazon.com/Mel-Bay-Antho.../dp/0871665174
This book also starts at the beginning, and uses exercises as a way to lead into playing tunes. Mostly folk tunes, with some very interesting and tricky arrangements.
I like these books that have more than just the tab to a song. A lot of the fingerings and picking patterns are still new to me, and having exercises as a way to lead into playing new material in the context of a song is very helpful.
I also picked up Saslow's ragtime book right after you did. I think it is great. I'm still toiling away on Ragtime Ramble and it's getting there. I'll be using that book for a long time!