My mother knows me very well, and one thing she does when I visit is that she finds and refers me to various random linguistics texts that she also sometimes pursues. She left a book on the floor of her guest room that was a big heavy text of Chinese historical linguistics, roughly.
Naturally, me being me, I picked it up and was reading it. I learned this morning that Chinese is full of substrata language traces, which is entirely plausible if one takes the time to think it through, but is not something I had ever thought about before. One very fascinating observation: the Cantonese "dialect" of Chinese shows strong lexical and even phonological traces of a non-sinitic, Thai-related substrata, which means that in some strange way, Cantonese is as closely related to Thai as it is to Mandarin (Beijing dialect). This makes perfect sense if you look at a map, but it's counterintuitive to the way that we normally like to think about Chinese linguistics. Not to imply that I know a lot about Chinese linguistics – I know next to zero, and what I do know is strictly theoretical, as in terms of actual speaking ability I'm lucky to be able to say "hello" – but it's quite interesting to me.