Books on Utilitarianism
For a concise introduction to utilitarianism I recommend Utilitarianism: A Very Short Introduction by Katarzyna de Lazari-Radek and Peter Singer (2017). This covers utilitarian history, the varieties of utilitarianism and arguments for and against.
A free introduction to utilitarianism is available on utilitarianism.net. This is a website sponsored by Effective Altruism and edited by Will MacAskill which provides comprehensive information structured as an on-line textbook.
For a more thorough treatment of issues around utilitarianism, an excellent book is The Point of View of the Universe: Sidgwick and Contemporary Ethics by Katarzyna de Lazari-Radek and Peter Singer (2014). Although partly structured as a discussion of the philosophy of the Victorian utilitarian philosopher Henry Sidgwick, it covers contemporary debates on major utilitarian issues and sets out Peter Singer’s considered conclusions.
Another excellent book is Moral Tribes: Emotion, Reason and The Gap Between Us and Them by Joshua Greene (2013). This argues that while common sense morality is appropriate for quick thinking within a group, for reflective thinking and for intra-group decisions utilitarianism is needed.
Finally, I recommend Happiness: Lessons From A New Science by Richard Layard (2005, 2nd Edition 2011). The book explores the use of life satisfaction surveys and other discoveries to improve lives.