I only have a few Embroidery Stitch Books. As the group progresses, I'm sure I'll hear form you all about more books. Below is a list of Embroidery Stitch books I have or I have had recommended to me.
The Craft of Crewel Embroidery. Erica Wilson. 1971. Charles Scribner's & Sons. This is the stitch book form my teen years & have schlepped it around for years.
Stitch Sampler. Lucinda Ganderton. 1999. DK Books. A more modern stitch book with colorful DK-style pictures. Well organized.
ANY of the Alabama Chanin Books, these are particularly relevant for this Study Group:
The Geometry of Hand-Sewing: A Romance in Stitches and Embroidery from Alabama Chanin and the School of Making. Natalie Chanin. 2017.
Alabama Studio Sewing + Design: A Guide to Hand-Sewing an Alabama Chanin Wardrobe. Natalie Chanin. 2012. Abrams Books.