Erica Jorgensen has just written the first UX book that focuses on content research. 

Strategic Content Design: Tools and Research Techniques for Better UX gives content designers a comprehensive guide to content-specific UX research techniques. 

Erica is on a mission to bring more respect to content to content practice. This book gives you the tools you need to show to your design, product, and engineering colleagues the usability and effectiveness of your content work.

https://ellessmedia.com/csi/erica-jorgensen/