Every year for the past several years Frederico Viticci at Macstories has been writing reviews of each new version of iOS just following it's release.
MacStories, as you might guess, is a website focusing on Apple products, software, and accessories. They do a nice job at all of that, and if you are interested in that sort of thing (I am, as one might guess) I can happily recommend the site for that purpose.
However, Frederico Viticci's iOS reviews are something very special indeed:
While it is called a "review", these articles could just as well be considered unofficial user's manuals for each new version of iOS. Frederico delves incredibly deeply into each new version of Apple's mobile operating system and describes, in detail, what is new and different, and how to use the new features, in addition to providing critique. If you've ever wanted to know how to get more out of your iPhone, iPad, or iPod Touch, or been uncertain whether the new version of the operating system could do a given thing, these articles are the way to get there.
At first blush the articles can seem intimidating - the review for iOS 10 is 30 pages long, and that's 30 web pages: Each page is on a specific topic, and is as long as the topic requires to cover. If it were a book (and if you are a MacStories club member, I believe you can get the review as a book) each page would essentially be a chapter. But the intimidation quickly dissipates when one realizes that the website actually has a table of contents for the article that lets you move through it at your own pace and allows you to quickly find and read the portions you are interested in when you want. Don't have an iPad? Skip the section on that device. Don't care about Apple Music right now? Move on to the next chapter.
The review is written very clearly, in language that is not overly technical or techie oriented - it is clearly intended to help guide everyday users in how to take better advantage of their devices. Frederico was in the vanguard of people determined to use their iPad as a primary computing device, and so had strong motivation early on to find ways to wring all of the functionality out of these machines. These articles have been incredibly helpful for me in my own travels down a similar path. I strongly recommend checking it out if you are interested in learning more about what your device can do.