Felt like it had been a while. I have another thread that was somewhat active on the book (link) and updated in January but having hit one of the original goals I had in learning at least some jazz fundamentals (notably, playing Eldon lines competently), thought I'd revisit the topic.
I think like a lot of people have said, this book for me was more a springboard into new paths than a method unto itself or whatever. I finished a big chunk all at once, then moved on to other things; a remote jazz workshop, in person lessons with a notable session/jazz player, discovering other players/teachers more into swing/Western swing. I finished the last 10% of it maybe six months ago, but stopped at the second half with standard notation.
Along the way I learned a fair bit about Jazz the genre without really setting out to or having many preconceptions. I wouldn't say I've become a devotee, just less ignorant. I know more about what I always liked (proper swing, early bebop), and still don't care for most showtunes or any scat whatsoever.
Less still do I like "guitar jazz," which is impressive but not anything I aspire to play, and to be honest I don't really enjoy listening to much of it either. I have learned a lot of songs that were previously "background music" off by heart as chord melody arrangements, many others besides, and a lot of it I really like. A lot of it I do not.
Anyway, it's a long way of getting to my point (at last!): I see this question asked here a lot, basically various permutations of "how do I get better at this thing." I'm not trying to be prescriptive, but having hit a long-term goal on the instrument, I felt like holding forth a smidge and maybe it'll help someone.
In my experience over the last year, I've had reaffirmed that if you're learning any "western" style of popular music (esp blues or country), you could do worse than spending some time on the basics of jazz. It'll require some work on technique, which I'd been at for 6-9 previous months, and obviously some work on theory (same); you'll have to do some investigating and listening on your own.
I've read a lot of people who are surely better guitarists than me say learning jazz is unnecessary for a guitarist "just" looking to enjoy, and maybe it is for them. But I feel like no guitarist got worse knowing more, and you can draw a straight line from jazz to 95% of what people learning the guitar want to play. You can certainly memorize a bunch of licks and patterns and shapes and learn theory without learning any jazz at all, but for me it re-contextualized a lot of familiar sounds. This made the "mimicry" of my ear even better while substantially improving my ability to play just about anywhere on the neck, several chords at that spot, etc.
Anyway, just my two cents. Happy as ever to have my opinions echoed, refuted, or improved upon. Cheers.