I have found The Sex-Starved Marriage by Michelle Weiner-Davis to be an excellent book to help both the higher- and lower-sex drive spouses to understand themselves, understand their spouses, and be inspired to work together to have a better marriage.
Weiner-Davis taught good active listening skills and coaching techniques that should help improve a whole relationship, not just the sexual aspect. She also shared openly about some of her own ups and downs in her marriage and interspersed some good case studies. This lady is one “bulldog of optimism” for marriages; especially for those marriages that look hopeless. I really appreciate that about her.