Academics sometimes publish popular books based on their own research, but not always cite properly themselves, even when book references other authors properly. Moreover, sometimes I can see that one author publishes very similar (but not same) papers on the same topic, without self-referencing, even though it can be seen that the author recycles some of hers/his ideas. Even respectable people in the profession do it.
Given this where is the line beyond which we are talking about self-plagiarism?
On one hand it feels bit wrong to do this even in a small amount. On the other hand I can imagine that it can be impractical, and cumbersome to piously self-reference yourself, and I also worry that that might seem egocentric to the reader.
It is no brainier that copying part of your old article, and submitting it as new is clearly wrong. On the other hand it does not seems to be wrong using the main ideas, quotes (or chapter titles), or paraphrasing minor ideas of your earlier papers to publish a book without using the same referencing standards for yourself as you use for other authors.
Any opinion on this? Should I always reference myself as well as I do others, or is it ok to be more lenient on yourself as long as it is not more excessive then it is usual in the field? Do you think that this depends mostly on the context?