Through running Happy Inbox, I have evaluated hundreds of newsletters. Newsletters are very much a matter of personal taste, but I have found that there are some key traits to great ones:
(1) Unique Content. Unique content is paramount to having subscribers that actually read and look forward to your newsletter. Recycling content published online won't cut it. A great newsletter should also anticipate how and where it will be read, be it in bed or in the middle of the work day, and optimize for that experience. The newsletter's content should offer a striking contrast to what a reader may get from anything else at that time, and it should leave the reader with a genuine sense of feeling informed, entertained, or connected. The Mattermark Daily—which shares the most significant startup analysis published each day—stands out from competitors by providing a thoughtful impression for each article it shares. The impressions are crafted so well that you feel the gravity of each piece and you understand how they add to the conversation. Politico's Playbook (the "Godfather of newsletters," if there were ever such a thing) and Capital New York's Playbook—which feature national and New York political news, respectively—provide an "insider" take on the latest political news early each morning. The insights are so fresh and respected that, as the New York Times described, "some of America’s most influential people will read [the Playbook] before they say a word to their spouses."
(2) Humanized. Adding a personal, human message to a newsletter is a great way to connect with readers. Product Hunt's newsletter nails this. In each edition, Product Hunt founder Ryan Hoover adds a little message that deviates from the newsletter's primary purpose, which is to share the top products posted to the site. His messages share everything from updates on his growing company to trends that the Product Hunt team is seeing. It's this personal touch and element of surprise that I believe gets people hooked to a newsletter—even if its minor and takes seconds to consume. To the contrary, newsletters that effortlessly share an RSS feed are unlikely to have engaged readers.
(3) Thoughtful Design. A newsletter's design need not be fancy or loaded with graphics to be great. The Playbook newsletters, for instance, simply contain paragraphs of text. But the basic design seems to be an almost intentional way of reinforcing that the Playbook contains pure insight—no nonsense. A great newsletter's design is more about what it shouldn't look like. It shouldn't look automatically generated (such as from an RSS feed), and it shouldn't have lackluster graphics. But the content must be extremely readable. After that, the possibilities are endless. I love newsletters that take the effort to give you visual cues as to how to read it, such as highlighting important information or boxing special messages. The Farnam Street newsletter, for instance, literally has a heading that says "Start Here" to guide readers on where to begin reading.
(4) Consistent Schedule. Preparing a great newsletter is not easy. It takes a lot of effort to incorporate unique content, a humanized component, and a great design into each newsletter you send. But the best newsletters meet all of these criteria while being delivered on a consistent schedule, without fail. Promising a daily newsletter yet having frequent spates of not sending it will ultimately result in reader mistrust and disengagement. You also risk missing out on the natural growth that a great and consistently delivered newsletter can experience. Dan Primack's Term Sheet and Connie Loizos's StrictlyVC excel at consistency. They rarely miss a day. But if they have to, they arrange for substitute authors—which has the added bonus of changing the rhythm and adding some excitement to an otherwise consistent newsletter experience.
For more great newsletters, check out Happy Inbox.