A typical book or website on the Jewish law of lashon hara (loosely translated as gossip) makes it seem as though no one can say anything negative about anyone, unless crime is involved. What makes this book special is that, rather than merely citing the most stringent possible views, Feldman discusses a variety of uncertain issues, and emphasizes that we must be "responsible for the quality of our judgment calls" and that knowing when to speak negatively involves "a lifetime of living and learning."
Feldman begins by discussing the logic behind the rule against even true negative speech. He suggests that seemingly true speech can be misleading, both because the speaker's view of a situation is infected by a variety of cognitive biases, and because the listener's interpretation of speech is equally unreliable. So even a technically true statement is easily misinterpreted.
But rather than merely saying no, Feldman guides the reader through a variety of difficult situations. For example, he discusses various situations where negative speech might be permissible for a legitimate purpose. For example:
*If you know someone who is marrying someone you know, when should you bring up their negative traits? On the one hand, if you say too much when a couple starts dating, you risk encouraging people to break up for minor reasons, reasons which (if each person dated longer and had a more complete picture of the other) might not justify foregoing marriage. But on the other hand, if you say something negative right as people are about to get married, you might cause more emotional pain because the couple is more invested in their relationship.
*Is negative speech as part of therapy permissible? Feldman says yes, because of the benefit to the speaker. This is the case even if the conversation is with a friend or relative rather than with a professional. On the other hand, merely venting one's anger may not always be productive.