I'll give it a try, though I don't really like manga for entertainment, so I guess it will be a bit difficult to keep me focused for studying :p Thanks a lot

Yeah, I know... :-) I have to credit the PostgreSQL core developers, you know: people experts in DBMS developments %-) They talked about it on the mailing lists almost ten years ago and I was intrigued. Since then, I probably have bought about 20 of them to distribute among colleagues or co-developers. For non-programmers who learned and created business applications with MS Excel, MS Access or Google Sheets, it was a gentle approach to relational databases and SQL, and helped a lot to migrate those solutions to (real) DBMS or ERP.