This is perhaps the only sequel for the basic self-study Dutch courses available out there. At least I found no other titles when I was looking for something to help me go on with my studies. So, Colloquial Dutch 2 seems to fill a market gap that would otherwise let students down. Unfortunately, the course falls short of what it could have been. I would even say that it fails on all main counts.
A good language course should have a progressive content. In other words, what you learn in Chapter 2 should build on what you learned in Chapter 1 and prepare you to face Chapter 3. Besides, texts should be chosen according to chapter level and illustrate the grammar under study.
This course does nothing of that. Most texts are directly taken from newspapers and other sources, with no interest in introducing the language language systematically. Texts at the end of the book are not necessarily harder to read than those at the beginning. More serious than that, however, is the fact that they are not presented so as to illustrate any particular language structures. You read them and that is all. There are no exercises to allow students to put new constructions to practice or to absorb the grammar. Such exercises as follow the texts are focused rather on the content than on the language, so that you will be asked to remember facts and tell whether assertions are true or false. At most such exercises will lead you to re-read a paragraph; they are rather tests of memory than of language acquisition. As a result, the only advantage such texts have over any online text out there is that they come with audio.
2) GRAMMAR SECTIONS
There are sections devoted to grammar, but they are often out of sync with the texts. Texts demanding a reasonable command of grammar are often found side by side with a grammar box explaining very basic principles. If you need such explanation, you probably won't be able to read the text. And if you are able to read the text, then the explanation is inane. Moreover, these grammar sections also come with few or no exercises.
3) THE AUDIO
There are also audio exercises, but they do not level well with the written material. The very first exercise involves the use of the imperative, which will be explained in the book only two chapters ahead. It also expects the student to hear a sentence, understand it, memorise it and repeat it while changing the verb mood. The book, at that point, is still discussing personal pronouns. Here too, if the student is able to handle the audio, they won't need the text; and if they need to re-learn personal pronouns, then there is no way they will understand the audio to begin with.
So, if you are really looking for a sequel, I think you will have to make do with this one. But if you find anything else out there, I encourage you to give it a good look. Chances are that it will be better than Colloquial Dutch 2.