Did you ever buy an instruction book that contained some legitimate music but not much in the way of new information? Perhaps the author(s) could have explained special things about the style or give hints about difficult passages ?
Then too, the people who assemble the books are perhaps better musicians than authors and not teachers.
If you get a book with almost all music, all you will have accomplished is a test of your sight reading without a valuable jump in your musical education.

So ........ why bother to say all that ? There is actually one book I have ever bought which should be a model for all others. The author spends much time on clear instruction and only enough music is included to make his point. I would say the book is "intermediate" in difficulty but even a beginner can benefit with the tempo backed off.

I have included a scan of the index. (You can tell that the man is for real.)
The book is "Fiddler Player's Guide to Jamming". Mel Bay.

PS There's a CD also but I would buy the book just to read it if I had to