The Legal Theory Bookworm recommends Speech Matters: On Lying, Morality, and the Law (Carl G. Hempel Lecture) by by Seana Valentine Shiffrin. Here is a description:
To understand one another as individuals and to fulfill the moral duties that require such understanding, we must communicate with each other. We must also maintain protected channels that render reliable communication possible, a demand that, Seana Shiffrin argues, yields a prohibition against lying and requires protection for free speech. This book makes a distinctive philosophical argument for the wrong of the lie and provides an original account of its difference from the wrong of deception.
Drawing on legal as well as philosophical arguments, the book defends a series of notable claims--that you may not lie about everything to the "murderer at the door," that you have reasons to keep promises offered under duress, that lies are not protected by free speech, that police subvert their mission when they lie to suspects, and that scholars undermine their goals when they lie to research subjects.
Many philosophers start to craft moral exceptions to demands for sincerity and fidelity when they confront wrongdoers, the pressures of non-ideal circumstances, or the achievement of morally substantial ends. But Shiffrin consistently resists this sort of exceptionalism, arguing that maintaining a strong basis for trust and reliable communication through practices of sincerity, fidelity, and respecting free speech is an essential aspect of ensuring the conditions for moral progress, including our rehabilitation of and moral reconciliation with wrongdoers.
And from the reviews:
"This very important book will be mandatory reading for legal scholars interested in duress, for philosophers and others concerned with lying, and for legal, philosophical, and political theorists who examine questions of freedom of speech. Shiffrin's arguments for the individual and community importance of sincerity are novel and effective. Her analysis of lying, her philosophical approach to questions of duress, and her connections between a theory of freedom of speech and the idea of freedom of thought all go beyond the existing literature. This is an impressive work."--Frederick Schauer, University of Virginia
"This book makes a compelling case for the importance of both veracity and freedom of speech for moral agency and progress. Full of insight and with a distinctive moral tone, this is a very significant contribution from one of the field's most distinguished and original participants."--Liam Murphy, New York University