Although the title says it is a tale of two mothers, it focuses more on one than the other, but that's okay, they have plenty of hot sex between them. The story mainly focuses on a busty single mother whose well-endowed son can't stop pleasuring himself. She tries to stop him, but ends up having sex with him, and it goes downhill from there for her.
Concerned about the inappropriate nature of her relationship with her son, she sends him to a female therapist, only this one is more concerned about getting it on with him than helping him with his "problem". This leads her to seduce her own son, a rather well-endowed young man in his own right, and by the end all four them end up in an orgy.
The sex is predominantly straight, though there is a scene between the two women. If incestuous stories don't bother you then get it, you won't be disappointed.