I picked this up as my last book in my initial reading of the "Throne of Glass" series.
"The Assassin's Blade" is a collection of five novellas that take place before "Throne of Glass" begins. This collection allows the reader to get a better understanding of Celaena's character and see where she came from and why she is fighting so hard to make the world better.
Upon finishing this book, I wish I could go back and read this one before I started the entire series. I knew this was a collection of novellas from the Throne of Glass world, but I was not expecting this book to have such important backstories for several of the plotlines in the "Throne of Glass" series. Though this is not essential to read, I do think this was one of my favorite books in the series.
My favorite short story was the last one: "The Assassin and the Empire". This story was so devastatingly beautiful and heartbreaking, I did not want it to ever end. Celaena is such a fierce main character, and I loved seeing how she ended up in the mines as a slave.
I HIGHLY recommend this book, and I HIGHLY recommend you read this before you start the entire series.