'Ahsoka' is a Disney Canon novel published in 2016 - but one that I read just now. It fills in the bits of Ahsoka's story from her escape from Order 66 to her taking on the mantle of 'Fulcrum', whom we see in Rebels.
If you are not familiar with the character, here is a short introduction. Ahsoka Tano became Anakin Skywalker's Padawan in The Clone Wars animated movie and series. Her introduction was controversial, but soon, she won over fans due to her plucky nature and her snippy attitude with Anakin. In later seasons, Ahsoka left the Jedi Order. Her next canonical appearance is in the Rebels animation series, where she is older and leading a resistance against the Empire. Post-that she made her appearance in an episode of 'The Mandalorian'.
This book is a mixed bag.
On the positive side, this portion of Ahsoka's life has been a mystery, and many a Star Wars fan will be happy to know what she was up to during the Empire's takeover, myself included.
The book also delves into her frustration between upholding the Jedi Order's ideals versus the Order's actions in the Clone Wars. We see the logical conclusion of this dilemma, which started when Padawan Bariss framed her and made her question what the Jedi were doing. There are also appearances and references to many characters from all across the Star Wars universe.
But that said, there is plenty that needs improvement too.
For one, the book is too short. Then, there is a love story element that is out of place and doesn't go anywhere. Finally, most of the book's essential beats have been set up earlier - so the book does not have much to offer beyond filling in some of the missing portions of Ahsoka's story.
In conclusion, if you are a fan of the character, this book will probably appeal to you. For others, it is average and is best read if there isn't anything else available.