The 'Thrawn' trilogy is essential. It not only brings back the beloved character of Thrawn but also weaves a complex and engaging story that ties in with the larger 'Star Wars' universe. The novels explore Thrawn's military campaigns against the New Republic and his unique way of analyzing his enemies.
A really interesting one is 'Kenobi'. It focuses on Obi - Wan Kenobi's time on Tatooine. It gives readers a look at his life in exile, his thoughts, and how he still manages to be a force for good even in his self - imposed isolation. It also has some great encounters with the local Tatooine population and a few brushes with the Empire.
Definitely. 'Revenge of the Sith' novelization is a great one. It adds more depth to the events of the movie. It details Anakin's fall to the Dark Side in a more nuanced way, with additional internal monologues and character interactions that the movie might not have had time to fully explore.