I've recently completed my Master's Thesis (and I'm a little proud of it). I'm interested in publishing my findings in a journal, but I'd also like to expand on my ideas and write a book for a wider audience. Is this an acceptable thing to do? I don't want to shoot myself in the foot.
For context, I haven't initiated the process of publishing the book version or of being published in a journal, yet. I simply would like to figure out what to do before I make any major decisons.
Publishing a book that incorporates and expands on previously published work in a journal is common in academia. You will have to cite the previous publication properly.
If you want to directly quote the previous publication or include it as chapter you may need permission to reproduce.
If you publish your thesis as a book, yourself or with a publisher, and it is the first time that it appears as a publication, then you can copy freely without citation. This assumes that the university doesn't somehow "publish" your work. The university will probably give you advice on how to proceed.
But, once it appears, then the correct way to work is to cite the older work as needed and to quote your old work properly. The best way to think of it, once it has already appeared, is to treat it just as you would the work of any other author. If you give up copyright to a journal, then you also are limited by the length of any quotes so as to avoid copyright infringement.
Self plagiarism and copyright are separate issues and you should explore both. The first is about words (specific expression) but the latter is about the ideas, even if paraphrased. So, you need to cite even your own published ideas.
However, with respect to the topic itself, you are free to publish other things, in particular, extensions of the older work. It is the words that need to be quoted and the ideas that need to be cited.
I'll also warn you that a self published book is probably a mistake unless you are already well established. Very few people will be able to find it and it is unlikely to be cited. Working with a publisher is a better bet, but they have their own ideas about what they want to publish.
For most young academics and those hoping to become academics, publishing in journals is the best path since you get some editing/reviewing help (also with books), but the publication itself has some visibility.
