Han Solo trilogy bar none. Daley nails Star Wars so well that he later wrote the radio drama that I hold as the equal to the OT.
The later solo trilogy is pretty fun, and the Lando novels are good old fashioned sci-fi.
The Thrawn trilogy is the benchmark and afterwards its very hit or miss and up to reader preferences. There are also a great number of good prequel novels and excellent stories under the junior scholastic banner.