Thank you for pointing that out, you are right. I had intended to complement with dates with 3 bullet points and missed that fine point.

2.5 era: " ... some might argue that the third era was the “Effective” era, with books such as Meyers’ Effective C++, Bloch’s Effective Java or Wagner’s Effective C# as flagship examples. But I consider these books, as useful as they are, just an offspring of the second era; a much needed upgrade. Let’s say, then, it was the 2.5 era of programming books".

3.0 era: "... at a time where the dot-com boom opened the door for new ideas, right in the middle of the Web 2.0 craze, and right before the rise of the smartphone and social media. Through the use of comic images, unusual text layout, and a fantastic sense of humor, Kathy Sierra argues, readers can learn the concepts easier; tricking the brain into the proper levels of dopamine".

At barnes & nobles / borders I always grabbed one of these books which made content enjoyable to read. She sparked a new era of genres produced by other authors, for example, an anime version of learning python.