If you are new to stitching and interested learning Sashiko and Boro, this is a good place to start. But also, if you have been sashiko stitching for some time and would like to know more about it, this is interesting to read, has lots of details and photos to help with technique, and a selection of really good projects that are not beginner level necessarily, but you can get there!
Boro & Sashiko, Harmonious Imperfection, The Art of Japanese Mending & Stitching by Sannon & Jason Mullet-Bowlsby
171 pages, softcover.
Open since 2005, but currently online only, A Threaded Needle is located in British Columbia, Canada. I am always happy to hear from you by e-mail firstname.lastname@example.org