This is a good book. The author was one of the experts on the topic until his death.
It is well written and not too long. If you like to browse books rather than read them through, you will find the chapter divisions, anecdotes, and "exercises for the reader" to be useful.
Seibert says that "playful curiousity" is a good habit to cultivate, because it keeps you focused on the present and immediate future, and on what you can control.
He also says that "bi-phasic" personality style can be helpful. If you always behave the same way, that can lead to getting you into trouble.
Thus, you would be better off not "always talking to strangers," or "never talking to strangers," but sometimes doing so and sometimes not.
"Good children" who grow up to be a good adults, and who always obey the rules and work to please their parents and authority figures, can in fact be handicapped relative to those who at times rebelled and engaged in controlled defiance: stealing, drinking/doing drugs, staying out, exploring their sexuality even when it was a no-no.
I'll end on this note: his point about the "good child" having trouble in certain circumstances reminds me of the book _castles burning: a child's life in war_ by magda denes, a little hungarian jewish girl who survived the holocaust (as is usually the case) in part through sheer luck. but if you read _castles burning_ you also get the sense of little magda as "insolent, impossibly sarcastic, and far too smart for her own good!" as her exasperated mother called her.