...According to a Tang soo do book online have, the art is 'uniquely Korean'. But when I ordered a book by Gichin Funakoshi, which was originally written much earlier than the Tang soo do book, I quickly realised they were pretty much one and the same...

I have to say that while there are alot of similarities, there are alot of differences as well... Yes TSD does have alot of it's roots in Shotokan karate (after all Gichin Funakoshi -> Lee Won Kuk -> Hwang Kee) added to that there are only so many ways to punch and kick, but there are differences as well... The use of hips, kicks, stances, movements are more circular, the and the forms (some forms have subtle changes, some are quite different) to name a few... (and of course the language)...

This is just my view based on studying both arts over the years...

Oh!! I knew it!! I just began my Tang Soo Do journey, originally training in Shorin Ryu. My first thought was, oh, this is the same thing, just different.

Luckily, I’ve looked into Shotokan quite a bit while I was looking into all the different styles of Okinawan/Japanese karate. I very quickly saw that Tang Soo Do is far more similar to Shotokan than Shorin Ryu, regardless of the fact that both Shotokan and Tang Soo Do have pretty much stemmed from Shorin Ryu anyway. If that’s incorrect, someone please tell me!

As for cross training or not, TSD came from Shotokan - why not explore the roots? You’ll still be practicing your original art, just a little different and with different words/names. If it ends up being a positive experience, then now you have a deeper understanding of your style! If you end up hating it, then simply go back home to your original style

So happy I came across this post!