Should I cite a book that I read to prepare for a talk but did not directly use it? I have used a few books and articles to prepare for a talk, but I only used some of them directly in my slides. The slides also include parts that are made based my knowledge (background knowledge plus what I learned from reading those sources) but are not new information and could be found in those sources. 

Should I cite all of those sources in my references slide? If yes, do I need to reference each piece of material on the slide, or just citing the sources at the end would be enough if I didn't use them directly?

NOTE My question is not a duplication this because that question is asking about referencing for presentation in general, but my question is not about referencing the sources I used directly, but those I read to build up my knowledge for the presentation but did not use directly.
What is the purpose of your talk?


If you are reporting progress of your work, focus on your work. In that case it is typically not relevant which general resources you used to brush up your understanding of the topic. 
If the purpose is at least partially teaching, I'd put them into a "Recommended Reading" slide / part of a slide at the end of the presentation.