The Scottish Mandolin Tutor by David (Dagger) Gordon. A great book of Scottish mandolin tunes with lots of playing tips. Using new and old tunes David has recorded a CD to go with the book with an example of how to play each tune and helpful guidance on Scottish mandolin playing styles.
There is also a section on mandolin chording. As well as the CD of all the tunes there are free online video files to demonstrate the techniques visually.