Anyway here's my treatise on why Warbreaker is actually the best entry book for the Cosmere:
It's a standalone novel (for now!!)
While having lots of greater Cosmere ties, it can be read without needing any knowledge of the lore or major players
Strong characters and character arcs
Really gives you a feel for the Sanderson style so you'll know whether or not his other books are for you without needing to commit to a whole series
Really fun worldbuilding and magic
I do mean fun, btw. The main two princesses, Siri and Vivenna, have magical hair that changes color and length depending upon mood and whim, respectively. Also a magic talking sword that was Made Wrong but just wants to be the Goodest Boy (gender neutral). The magic itself...I shan't spoil but it is also very interesting
Sanderson isn't the best at romance but the fact that he tried to write a love story in this book for his wife makes it more romantic by default imo
The early clunkiness/debut energy that's present in Elantris has been smoothly ironed out. I like Elantris quite a bit as a novel but I don't find it a successful lure into the greater universe, tbh
Who doesn't love a bitchy, cranky old man as one of your primary protagonists
Thank you for coming to my Ted Talk