Best thing for getting stuff into your head: https://www.goodreads.com/book/show/1250623.How_to_Develop_a... Much like weight lifting, following this book will give you specific memorisation techniques which can be useful, but also results in a general strengthening of memory, even when you don't use any of the exact techniques). It also strengthens your ability to imagine things, and hold those images or arrangements in your head, which is useful for applying mental models you've learnt.

https://www.goodreads.com/book/show/9793361-the-decision-boo... Not the best, and I only really use the first one in the book (Eisenhower Matrix), but I found that alone to be worth the price (you could just google that one though). The rest of it is useful as examples of the wide variety of model types and types of things that can be modelled.

Thinking in Systems: A Primer, is a great book that I highly recommend. It's one of those books that serves as a great introduction to the subject of creating models of systems, and it's neither too long, nor overly specific on any particular subject. By the end of it, you'll know roughly enough to be able to know what you want to know next, in regards to system models. https://www.goodreads.com/book/show/3828902-thinking-in-syst...

This blog post is more like a reference resource, and I think it's worth looking over and picking out whatever interests you: https://medium.com/@yegg/mental-models-i-find-repeatedly-use...

EDIT: because my formatting was atrocious.