The book is not a blog; it is not published step by step, but as a whole, at the same time.

Therefore, I suggest removing comments like "Continued in next post" or "Followup to"; especially if it is a reference to the very next or very previous chapter, but also if it is two chapters behind. Specifically, chapters 3 and 4, 11 and 13, 20 and 22, 22 and 23, 28 and 29, 31 and 32, 31+32 and 34, 41 and 42, 49 and 50, 54 and 55, 56 and 57, 57 and 58, 59 and 60, 60 and 61, 62 and 63, 63 and 64, 64 and 65, 64 and 66... okay, I guess you get the idea. In a book, the next chapter being a followup to the previous chapter is pretty much expected.

On the other hand, chapters 16, 18, 28... are followups to chapters not included in the book. Maybe instead of "followup" it would be better to use some other words to express that this chapter is related to some online article.

Summary: the book is a different medium, so I suggest rewriting the standard "followup" notice, depending on situation:

• it it's a followup to the previous chapter (maybe also two chapter behind), just remove it;
• if it's a followup more chapters behind, use the full sentence to explain it;
• if it's a followup to something not included in the book, again use the full sentence, but a different one.