Dr. Helen highlights some sexist dating advice. I think the commenters have it right. Most self-help books are aimed at women and as such, have a female bias, because most men don't read self-help books (usually).
Aside from sexist books, as a general principle, like attracts like. Bitter attracts bitter. Angry attracts angry. Happy attracts happy. Ambitious attracts ambitious. On and on it goes. So, for better or for worse, the person a person is in a relationship with is a reflection of that person on some level. Usually, the people share some fundamental beliefs about the world. But people do change, and I suspect, that this is where difficulties in relationships can arise.
As far as dating the divorced, Roger L. Simon had the best advice in the comments:
The problem as I see it is that common sense ain't so common and people assume because it's easier than looking in the mirror.
“Frankly, it’s self-evident to me that women are the more selfish of the sexes.”
Frankly, it’s self-evident to me [who else?] that human beings are human beings.
Leaving that behind, as a twice divorced man with children who dated a fair number of terrific and some not so terrific women, both divorced and single, I know I did one thing right: I didn’t waste a single second reading a self-help book of any kind. I just used common sense and didn’t make assumptions about anybody.
H/T Conservative Grapevine