This book is now back in stock at https://redcowmusic.co.uk/product/contemplating-the-concertina/
If you’re an intermediate or better English concertina player with a good grasp of music theory who wants to move beyond “session tunes” into more complex music and playing techniques, this is definitely the book for you. Be warned: on the very first page of tuition Mr Atlas will have you playing a scale of C# Major in six sharps, as an exercise to familiarise yourself with the enharmonic accidental buttons which the odds are you’ll never have touched before.
If you’re prepared to put the work in, this book will teach you a LOT, but you will have to put in a lot to achieve that.
The only book on the market today which teaches advanced playing techniques. Highly recommended!