I bought this book for my (not very interested) son, who plays viola.
The book has all the tunes written out 2 ways- in alto (viola) clef, and in treble clef. The arrangements are basic, and there is a pretty good selection of fiddle tunes.

If you already play violin/fiddle and read music, you can play the tunes as written in the treble clef version. The problem is -the tunes will be a fifth lower (eg, even though the music is written in "G", you will be playing it in "C". If you read alto clef, and play them as written, you will get the same result. The tunes work on the viola, but they are not in the "right" key.

You can play solo, or you can everyone else to try to change key to play with you, but the problem is that the viola doesn't easily allow you to play in the standard key w/ other people unless you play an octave up and use positions to get the F,G, A and B notes normally played on a violin E string. Does that make sense?

Sharon